Key West:Boyds Campgound in Key West has a couple of spots you could use your camper and pull your boat up next to it.

Delray Beach:
There is no camping anywhere around Delray Beach.

West Palm Beach:
Peanut Island is just inside the Palm Beach Inlet and allows tent camping. There is no bridge to the island so you have to launch from Phil Foster Park which is only about 100 yards from the island. Phil Foster park has an area to launch non Motorized vessels (catamarans). There is good sailing in the lake/Intercostal waterway or you could just go out the inlet to get in the Atlantic. There are a few Tiki Bars along the coast (Singer Island). There are showers on Peanut Island and they offer both reserved camping (Small Fee) or "primitive camping" (free). You can pull your sailboat right up to the tent in the primitive camping but not the reserved camping. There is also a water taxi that makes regular stops on the island.
Peanut Island website: http://www.pbcgov.com/parks/peanutisland/