Gary, if you're able to travel further up the East Coast, might I suggest a cruise to eastern Canada? Carnival Victory does a few 5-night runs to Halifax and Saint John in the summer, round trip from New York. I can speak from first-hand experience that this is a very enjoyable cruise.
Another wonderful choice is Bermuda. Carnival does not offer a Bermuda cruise in the summer, but several other lines do, from several cities along the East Coast.