The cars have 3 bench seats that will seat 2 adults each. If a child is small, 2 adults with a child in between would fit tightly.
When we went in January as a group of 11, we were seated in 2 cars. When we checked in, we had the option of being seated quickly in 2 cars that were not side by side or we could wait until we could get 2 cars side by side. Since January is not a busy time, we opted to wait for 2 side by side, but I'm sure that at busier times, they would not have offered that option.
With a group of 10 you will probably get one full car and then the first two seats in a second car, with a pair of "hitchhikers" put in the 3rd seat at some point during your meal. I would not count on the 2 cars being side by side. It doesn't matter much anyway as it is rather difficult to converse in there.