I've been able to do that in my '07 Sedona, although I usually have two FF and one RF, so I put one of the FF kids in back so they can climb through the hatch and into their seat without being lifted. Easier on my back. But I can see that might make things more complicated with two RF's in the captain's chairs.
It's definitely possible to do it the way you're thinking... does your Sedona have the 60/40 split on the back bench? If you fold the 40% side down and install on the 60% side, that gives you a bit of space to stand so you can get the baby buckled in.
Alternatively, you could put the baby RF in a captain's chair, fold down the other captain's chair, and put the older two (RF and FF) on the back bench. I've used that configuration before and it's nice because the older kids can climb into their seats and you can just sneak past the folded chair and have plenty of room to buckle them.