We had an ADR last trip and when we got there, they tried to give us a picnic table. We told them we wanted a car so we had to wait another 30 min.If you have an ADR you will be seated in a car. The picnic tables at the back are traditionally used for "walk up" guests who didn't have a standing ADR.
You will share a car with strangers though. You could be seated in any of the seats with strangers in the others. Our party of two has been seated in front, in back and even in the middle with two other stranger couples.