At Assateague,we stayed in the NP Bayside loop 3 site C48.It is a huge lot with a tree for shade and direct access to the bay.It is also fairly close to the dump station and water hydrant.Loop C also allows generators at certain times.No hookups but it's worth it IMO to be in the park.And get a schedule and go to all the ranger programs.They are great!
As to Outer Banks,I would suggest NPS Frisco Campground at least for a day or 2.Again,no hookups but lots of room between sites and close to the beach.
