Tail end of hurricane season, OBX not where you want to be if a storm comes through. If so, make sure you bail out early. I wouldn't be wanting to cross those bridges in a storm. Our trip back from Rodanthe last year was in 30 mph winds and the trip across the 158 bridge was white knuckle.
Hatteras KOA has several sites right on the back side of the dune. There's really no waterfront. Camp Hatteras is the same.
Further up, there are a couple of RV parks in Kitty Hawk. That part of the OBX has more stuff (stores etc).
We enjoyed the OBX in May.