"Car seat" in the US means an extra seat for infants that go on top of the car's native seat.

https://www.amazon.com/baby-infants-car-seats-booster/b?ie=U...

My guess is child seats.

Fair enough. It's high time that car manufacturers worked out how to make seats/seatbelts that are adaptable to all ages. Or perhaps some sort of foldaway "wings" which turn a standard seat into a child seat.

So his children can sit in them in the next car.