I have been taking my summer vacation at Bethany Beach with my family (wife and 2 young boys) for the past 5 years and had a wonderful time each and every year. The beach is extremely clean, lifeguards are very professional, and the kids just love everything about it. One thing to know however is that waves are relatively strong (for the East coast, at least) and there are significant rip currents you need to watch out for. The Sea Colony resort, located South of Bethany Beach, offers over a dozen pools, tennis courts and shuttle service to their mile-long private beach. It is a very interesting option for families with young children. I recommend you look for townhouses located West of road 1, as the seaside condos are very expensive in the summer.