Here's my story (so far) of tandem wearing, in case it helps anyone. Of course there are lots of other ways to do this--I'm not trying to say it's the only way, but I thought I'd put this out there just the same. (I also posted a version of this on thebabywearer.com--sorry for the duplication.)
My little girl was born when my big boy was 3 years 4 months. I had a c-section with her, so while I wore her right away (12 hours after the birth), I didn't wear him until four weeks after the birth. I tandem wore for very short periods (melt-downs/snuggles) around the house when my newborn was 4-5 weeks, but then I started tandeming in earnest--often as a mode of transportation--once I was 6 weeks pp and feeling really good.
If you tandem, be sure to PRACTICE in the house before going out like this! What works best for one mama might not work for another, and you should find out what works or doesn't work for you before you're far from home.
My personal criteria:
baby has to be on front, big kid on back
carrier for baby should be put on first, since baby will stay up longer and big kid go down to walk some
big kid carrier has to be easy enough to put on without bending over a ton
big kid carrier has to be small enough to stick in my bag and carry while he walks and/or leave on my body while he walks
A day in the life. . .
Today, for example, I got up at 7:00, got dressed, unloaded the dishwasher, started some laundry, and got my son breakfast while my husband changed the baby's diaper and got her dressed. When he brought her up front, I popped her in a sling and headed out to walk and take a bus to drop my son at preschool, him walking hand-in-hand with me. I changed a diaper at the preschool before reading my son a couple books and saying goodbye, and then (baby in a sling again) I walked down the street to the other end of campus to meet with a colleague. While we got started and just were chatting, I nursed, and then I put the baby in a mei tai on my back and she fell asleep. She napped for two hours, as I sat and typed and talked with my colleague (we're working on the second edition of a book and meet weekly to write and revise). When the baby stirred, I brought her down from my back, switched her to my front in a sling, gathered my things, and left. I took a bus straight from my colleague's office to the Whole Foods near my house, and sat down at a table in the sun outside the store to nurse. Baby went back into the sling and I went inside to do my food shopping. After I was done, I walked the few blocks home and had a quick lunch. I popped her out of the sling to play on the floor a bit while I had lunch, then I changed a diaper and put her back in. I had just put the laundry into the dryer when the Whole Foods delivery person arrived on her cargo bike with my groceries; I buzzed her up and she left the groceries in bags on the floor of my kitchen. I sat down on the couch, took baby out of the sling, and nursed her again. She was almost asleep, so I quickly buckled on a baby-sized soft-structured carrier and put her up on my back, where she napped again while I sorted and put away the groceries, put away the dishes, started dinner, and baked brownies. When she woke up and shifted around, I went back to the couch and nursed her, and then gave her some floor time while I folded laundry and did something on the computer. Then I put her in the sling again to put the laundry away and clean up the kitchen. Back out for a little more happy squealing floor time while I checked my lists, then I nursed her again and popped her back in the sling, where she immediately fell asleep, to go walk and take the bus to pick up my son from preschool. Once I picked him up, we walked across the street to the bus stop and took the bus home. I took the baby out of the sling to play on my lap as we sat in the sun and waited for the bus home, then put her back in for the bus ride. Getting off the bus, I put my son on my back in a big-kid soft-structured carrier, and we walked home together. At home I put my son down for him to have a snack and play, and switched the baby to the baby-sized soft-structured carrier on my back to put some things away, finish making dinner, and get my son fed. I took her out to sit down on the couch and nurse her again. After that my son wanted some cuddle time, so I put him on my back in the bigger soft-structured carrier and the baby on my front in a sling again. When my husband came home from work, I took both kids down and he held the baby and played with her while I put some things away around the house, and then I sat down and nursed her again. She fell asleep on my lap; my husband held her, still sleeping, while I put our son to bed; then I held her again, nursed her some more, and she fell asleep again on my chest. I popped her into a sling and sat on the couch watching a movie with my husband for a couple hours. After the movie ended, I brought the baby into the bedroom and laid her down on my bed (arranged for safe co-sleeping, with a bedrail). She kept sleeping, and I went back to the living room with my husband for another hour or so before we both came back to bed too at midnight.
Pic. 1: This was comfy, but not ideal since baby went on 2nd yet generally stays up longer. I do this around the house if baby is playing on the floor, big kid wants snuggles, and then baby suddenly wants them too.
My favorite combo:
FCC (front-cross-carry) pre-tied in a long wrap on my front for the baby, with a buckle carrier/SSC (soft-structured carrier) on my back for the big kid
second choice: RS (ring sling) for the baby, but sometimes the rings interfere with SSC strap comfort
Pic. 2: My favorite!
Pic. 3: That's a ring sling. If I'm careful, it can work, but it takes more fiddling for me. I also tend to wear baby slightly in between tummy-to-tummy and hip-carry, so it's not perfectly symmetrical, which can throw me off when tandeming. But it's a great choice in warmer weather, since the sling covers less of my body.
Getting everyone up there:
I usually put on the wrap first (front carrier) and leave it on the whole time I'm out of the house. Wearing nursing shirts with empire-style openings means I don't have to unwrap at all during the day.
Then load in the baby (in part because if I'm out of the house I have nowhere to put a non-sitting baby while I load the big kid!)
Then put the SSC around my waist. My wrap "waist" strap is high since the baby is little, so the "waist" strap of the wrap is really about 2" under my breasts, and then SSC waist strap more by my natural waist/jeans.
Tuck baby's head under one of the rails on the wrap. I did this religiously when she was small (6-12 weeks) and not so much now (5 months). If she's awake she kind of leans back and looks like she's wondering what the heck is going on.
Get big kid up: if there's a bench nearby, or a wall/ledge/something, I have him stand on it, and I stand in front of him and bend just slightly and he sort of jumps up a bit to my back. It helps that I'm short. He knows to put his arms in for the adjustment process, too, while I pull the carrier up around him, then stand up as quickly as possible and adjust everything down from there. If there's no bench, or if he's melting down, I hip scoot. This was tricky to learn to do around the baby, but with practice I got it. Again, bend over as little as possible and stand up as fast as possible after he's on.
My considerations about choosing carriers:
MTs (mei tais) are doable for the baby, but if I need to nurse I have to get the big kid down, which is not ideal. For me, popable is way better.
No wrap or mei tai on back is ideal for me for big kid because I couldn't seem to master tying it without bending over a lot and disturbing the baby.
Wrap on front should be thin/flat/not bulky since more is going over it.
Knot for wrap on front needs to be in the front for easy adjustability even if someone's on my back and also so there's no knot in my big kid's stomach.
Different carriers in the same brand and same size weigh more/less than each other, depending on the kind of canvas or strap material used and the kind of body fabric used. I had a strong preference for lighter-weight carriers relative to heavier ones.
Choose carriers you know well for putting on your back, and check the straps (if SSCs) before putting on. when you've got a baby on your front is not the time to realize you need to let out a bunch of strap, etc.; I try to do all that before and then just load up.
Play around with the height of the chest strap if using an ssc on your back; I found I only needed to use the chest strap when my big kid on my back is sleeping (dead weight) or extra-leany; then I use a burp cloth over the chest clip to pad the baby's head.
Pic. 4: It was hard to maintain tension tying the MT without bending over too much/too far for the baby. If I knew the big kid would be up for awhile, I could do the MT or even a ruck first, but that generally doesn't happen for me. A ruck in a wrap also isn't a good choice for me for the big kid since then when he gets out, I have a bulky wrap to carry around, vs. an SSC I can just let dangle behind me if need be.
Pic. 5: showing the pad on the chest clip.
Dealing with clothing/outerwear/weather:
Good shoes are important. When people ask if this hurts my back, I can honestly say no. But I do feel it in my thighs after a day of going back and forth around town like this (kind of like a workout), and my feet were definitely hurting until I upgraded to a really comfortable medium-to-high-end pair of hiking sneakers with good insoles and good arch support. 50 extra pounds (plus the pregnancy weight I haven't lost--call that 20 pounds to be kind) is a lot of extra stress on your feet. Be good to your legs and feet!
I personally couldn't deal with a babywearing coat--or any coat, for that matter--while tandeming. It was way too hot and bulky, and also impossible to get over everyone without tears. If I went out wearing it and my big kid asked to go up, I'd have to take it off and carry it.
Instead, I got a few two-sizes-two-big hoodies, and put them on after baby is in the wrap, zip them up around her, and then put my big kid on my back over that. He can wear whatever jacket he needs for the day, and the baby can just wear inside clothes.
Pics. 6-8: different hoodies over baby. We went through the winter like this.
My contexts for tandem wearing:
Leaving the house and walking to the subway or bus in the morning when I'm in a hurry
Containing both kids on a crowded bus when I have to stand
Walking home from school, stores, parks, outings, or around Disneyworld, etc., when big kid is exhausted (though I personally try to avoid stairs while tandeming--it's just more stress on my legs/body than I like. A flight or two in the subway, no problem, but if there's an escalator, that's better, and the 4 flights up to my apartment? My big boy gets to go down and walk up unless he's totally comatose.)
Getting us all under one umbrella when it's raining and we have to walk
Cuddling around the house when two kids need hugs and snuggles or are melting down
Anytime I have 15-45 minutes and need a good leg workout and some double hugs. One could wear longer, in theory, but that's about my limit of practicality. I think, including a bus ride when my big kid fell asleep, I once tandem wore a bit longer than that, but generally it's around half an hour and then he wants to get down to do something else.
Pic. 9: staying dry!
Pics. 10-11: more pics of my favorite combo
Carrying stuff while tandeming:
Ideally we wouldn't, right? 50lbs of combined kid-weight (right now, for me, with my little one 5 months old and my big boy a fairly slim 3.9-year-old) is plenty.
But I'm car-free in the city, so I kind of have to. I like bags with cross-body soft straps, especially onbags (see pic. 13) since the bag will almost certainly go near my little one's face.
Soft-bodied bags are better, too, because they'll be hugging my side and I don't want anything banging against my big kid's foot.
I try to just bring the minimum stuff needed for 2-12 hours out of the house. for me, that's essentials (wallet/keys/phone), personal items (comb/chapstick/hairband/handcream/sunscreen stick/sunscreen wipe/tissues/hand wipes), snacks (bag of cereal, lara bar, squeeze pack of peanut butter, bottle of water), diaper stuff (we use sposies and are lucky that my big kid is out of dipes and reliable, so just 4 baby diapers/wipes/changing pad/baby change of clothes/ziploc bag for emergency wet clothes/small packs of alcohol hand sanitizer), my SSC when the big kid isn't in it (in my experience, ocahs with a topstitched waist fold up the smallest because you can squish the waist best), misc items (carabiner clip for extra bags/lunch boxes, my sun hat and the baby's sun hat, a few of those links for baby to hold, 6" inflatable beach ball as an emergency toy).
Pics. 12-13: different bags that work. The picture at the left is in Disneyworld, actually the very first time I tandemed outside of the house.
Video (sound quality not great--I didn't realize how loudly I needed to talk!--but you can see the motions anyway):
Showing how to get big kid on your back with baby on your front
Showing how to get big kid off your back with baby still on your front
Think you get some weird looks while wearing your baby? or your toddler? or preschooler? or wearing a leggy three-year-old while 8-9 months pregnant? Been there, done that. Those are nothing compared to this.
Surprisingly, a lot of people seem not to notice the big-kid legs if they first see me from the front, and then they do this hysterical double-take when they finally notice him on my back.
There are a lot of very positive comments, too. I've been told a number of times what a good mom I must be, how lucky my kids are, etc., and I definitely get the "you are as strong as a mother in my country! This is how we take care of our babies!" line from immigrants. One man gave me a big smile, then actually turned around and came back and told me he had to look at me again--he just couldn't believe how lucky I was, getting hugged from both sides like that, and that I was the picture of love. Um, yeah, kind of made my day.