I've done the 35 mile loop in the past, and 1 other ride from the event coordinators (WCBC); I have nothing negative to say about either.
It's mainly southern Delaware, so it will be relatively flat.
The MS Bike to the Bay is a nice ride at 35, 75 or 100miles (and ends in Dewy Beach, DE).
Return trip the next day is optional, if not can take the shuttle back Sat Night or Sunday AM.