If you are feeling adventurous you can stay at Cape Henlopen state park, Delaware Seashore park or Massey's landing and take the Lewes Ferry to Cape May and the Jersey Shore.
Further South in MD there is Assateaque State Park. Frontier town and Castaway's.
Rates for the private parks within the ocean/beach corridor are climbing through the roof. Nevertheless getting a site during peak season can be tough , I suggest you act now if your plans are for July.