Are you thinking PoE for the access points? Is the area wooded? Are the users content to hook-up to wired utilities for each parking? Are you worried about protecting from lightning related events?

I don't have any experience with this, but I worry a bit about getting reliable site WiFi through a metal enclosed vehicle.

One interesting approach, if the RV's routinely have power, is to hand each RV an Eero, or similar, with instructions: "Place this near a window facing the center of the compound." Hopefully, there are no metal shades or screens in the wireless path.