Assateague Island and south of there the Outer Banks. Best time to hit those spots is probably early/mid fall. I know we went late September to Assateague and the temps were hovering in the low 80's. No bugs and most importantly the large crowds weren't there.
FYI, Assateague is where the wild horses are if you've seen them mentioned before. South of there is Chincoteague, I thinks it's August they do a roundup each year. They cull some of the herd and drive them across the water off the island onto the mainland. Pretty spectacular scene.