I know that there is no reentry but can we get to the car nd have our lunch. Would we be able to get back in? What are the restaurant availability?

The parking lot is inside as what wynn said, so there is no need to leave the compound. So if you need to eat you can go back to your car and eat. I brought a small backpack with me and I put small snacks in there for when I got hungry while walking round I would have something to eat

Your car is in the center so yes There is a small cafe on the grounds There is a nice restaurant called Rats which we went to. It use to have access to the grounds but not since Covid.We asked at the gate as we left and they took our name and let us back in but no guarantee

The parking lots are on the grounds so you do not need to leave the park to access your car. As far as restaurant availability, I would advise checking the Rat's Restaurant website for information.