(I know your children are mostly old enough to do without, but just for everyone's information...)
The past couple of years we have taken a late flight to MCO, and when we got to EA there were very few cars left, mostly only premium cars and SUV's, and almost all of them Chevys.
Last fall we had to switch vehicles twice after we discovered that a carseat would not tightly secure in the car we chose.
My carseat has a warning in the instructions that recommends against using it with a seatbelt that is mounted forward of the bight. (The "bight" is the seam where the seat cushion meets the backrest cushion, BTW.) In cars where the seatbelt stem rises out of a slot in the seat cushion itself, it may not be possible to adequately secure a carseat. They are not kidding; it's darned near impossible with our E.Bauer highback booster. We ended up with a Chevy Blazer, and the fit was still not very good, but at least the belt rose at the proper angle to restrain the seat. Thanks to this problem it took us two hours to get out of the garage.
The moral of the story is that getting a much larger car than you anticipated may not be such a lucky break if you have to install a carseat. Most domestic premium/luxury cars have those forward-mounted seat belts.