We go to Camp Hatteras Resort & RV Park - The World Class RV Resort on the OBX several times each year. The nicest on the OBX for full hook ups. National Parks I would recommend are Oregon Inlet on the north end near Nags Head, Frisco which was just mentioned in Airstream Life and Ocracoke if you want to be removed totally and deal with the ferry.
We've been there early April.
Having Ocracoke to ourselves is like a little slice of heaven.
No bugs that time of year either!
The ocean is a little cold that time of year though.
Absolutely loved it!