I would not recommend any of the campgrounds, with the exception of one private one right next to Hatteras KOA. The name escapes me (Ocean Waves sounds familiar), but it doesn't matter, as it books solid early in the year. KOA is OK, clean, close to the Atlantic, but has the ambience of a Walmart parking lot. As previously posted, NC 12 can be congested during peak season. About 2hrs. to Duck(from the KOA) in summer.
Check with OBX visitors center for all campgrounds in the OBX area. The trip is worth the hassle, as the OBX are absolutely beautiful.