See: What cars make it easiest to securely install a child seat?
When I went shopping to replace a car with 200,000+ miles one of the things I checked on my overnight test drive was getting the car seats in and out and how much room was there with those installed? I also checked that the kids could see out of the side windows as some of the new car designs block the side view for kids.
The vehicle I chose is on the Consumer Reports list.