I'll chime in with the others - I've got a Sequoia and if I were looking at the carseats in the third row, I'd get a minivan.
We keep our carseats in the second row - third row access isn't good enough - even in the larger Sequoia - that I would want to get back there & strap a squirming kid in. If the kids are older and can buckle themselves up, that's probably a different story.
Edit: Just re-read your post - assuming the seats flip the same as the Sequoia, you should be able to fit two seats on row 2 and access the third row just fine. I'd put the kid that can strap themselves in on the third row, though. If the second row's *any* narrower than a Sequoia, you'll probably have a tough time getting two carseats on the non-flip part. Of course, it'll also depend on your carseats - the LATCH bases for pumpkin seats occupy more width than booster seats for older kids.