We camped there when I was a kid and my parents now have a house not far away. It's fun place to explore becuase it used to be a Navy base during WWII. There are all kind of old towers and bunkers (mostly covered over now, when I was a kid you could go inside them.)
I've seen vehicles on the beach around Rehoboth but I'm not sure about Cape Henlopen itself.
Another plus is that it is right next to the ferry to Cape May, NJ and that makes for a good day trip.