Delaware's beach week happens on a strip of sand so narrow at Indian River Inlet that, crossing the bridge, you get the Atlantic out one side of the windshield and Rehoboth Bay out the other. Delaware Seashore State Park has a campground on each bank of the inlet, north and south, and that's where a family rig settles in for the week, between the surf and the bay. A little farther up the coast, Cape Henlopen holds the pines and high dunes at the point where Delaware Bay meets the ocean.
The state is small enough that one site covers the whole shore. Leave the motorhome on its pad at the inlet, give a day to Cape Henlopen's bay beaches and another to the ocean side, and let the Rehoboth trolley handle town so nobody spends a summer afternoon hunting for somewhere to put a long rig. Pick one base, stay put, and drive the coast in both directions from it.
Delaware Seashore and Cape Henlopen campgrounds for a motorhome
The inlet campgrounds and Cape Henlopen are the sites that fill first on summer beach weekends, so the reservation comes before the rig. Delaware State Parks posts each campground's length limit and hookup level on its camping pages, and the site you land decides which class of motorhome makes sense. For two people with the beach week as the whole plan, a smaller vehicle widens the choice of sites, and the Delaware campervan page covers Cape Henlopen and Rehoboth that way.
Summer is the crunch on the coast, and the weather that can move a night is a hurricane week or a coastal storm blowing in off the ocean at the inlet. Inland near Laurel, Trap Pond's cypress swamp is the freshwater alternative to the shore, and it's written up on that same campervan page.
Lums Pond and the Chesapeake and Delaware Canal
Coming down from Pennsylvania, New Jersey or Maryland, the first night that makes sense is Lums Pond State Park near Bear, at the top of the state. The pond is still freshwater ringed by forest, with the Chesapeake and Delaware Canal alongside, and it's good water for a canoe or a fishing line on the evening you arrive. It also works as its own base for a couple of quieter days before the run to the coast, and the park's camping page has the length and hookup details for the loop you book.
The drive south crosses Kent County and passes Dover. On race weekends at Dover Motor Speedway, rigs fill the track's camping and the campgrounds around it, and the same dates pull motorhomes off the rental listings, so a beach trip that overlaps one has to book both sooner. Killens Pond near Felton is the quiet pond week in the middle of the state, and the Dover RV page covers the races and the pond.