We stayed at the Refuge Inn years ago. That was nice but a very different experience than say Ocean City.
I have only been to OC in the off season but extrapolating what it was like then (and seeing the 8 lanes of traffic) I think it would be too much for me in the summer.
The Bellmoor was going to be my suggestion too, with two caveats-- it's expensive and it's further from the beach than you might think (5-10 min walk.-- Rehoboth seems to have longer city blocks than NYC, so things that are 2blocs from the beach are far enough that you don't just pop back to your place).
Boardwalk Plaza looked like a possibility but haven't actually stayed there.