C.A.
My first question to you would be why do you need 2 carseats for one child? I don't understand that part. Did I misunderstand what you were trying to say?
My mom has a Equinox and you would only be able to fit 2 seats in the back comfortably. She has a 2006 and they have more room then the newer ones. My brother in law has one for his job and they are very tight. You would be able to fit a stroller and a dog if the stroller is not a big one. The dog needs room to move around. And as for the Saturn I wouldn't buy one if you paid me. My sister in law had one and she had it in the shop more then she drove it. If I were you I would look into a van. You could put two carseats in the middle, one in the 3rd row and have the dog in the 3rd row. Plus be able to put the stroller in the back with no problems. We looked at alot of options and that was our only choice and we only have one child as of right now. Everything else was just too small. I never thought that I would be a van person. I didn't want any part of a van but now that I do have one I wouldn't trade it for anything else. When we don't need the 3rd row we just put it down and we have plenty of storage area. I have a large stroller and still have plenty of room for groceries and other things. I love my van.
When going shopping measure your gargage to make sure that it will fit.