Hello: I'm sure others will respond to your questions as to what they are doing. But I wanted to say that we plan to put our car seat in the second row. We will only have the one, unless we bring a friend along, but either way, I don't see any reason why you couldn't have your car seats in the Captain's chairs in the second row. IF, the other passengers are willing to just walk between the two captain's chairs to get to the third row.
Otherwise, the chairs have the "easy glide" feature, where the seats will slide forward forward the front row, and the person can enter the third row that way. So, if you have a car seat on the seat, its not going to fold with the glide, obviously. I hope this is making sense! And you probably know all this already!! Just trying to help.
Also, will you have to buckle them in, or can they do it themselves? If you have to do it, just consider that you will have to climb in and back there each time!
Personally, we feel our daughter will be safer in the second row. Congrats on your Silver Acadia!