My parents live in Falmouth, MA on the Cape, so we spend a lot of time dow there in the Summer. Of course the beaches are great, my personal favorite is Old Silver in North Falmouth, though I haven’t been in years.
Surprisingly, we don’t actually spend much time at the beach as a family. Its a whole to do, getting everyone ready, working around nap time, bringing enough food and keeping the water cold, hauling the beach toys and chairs and towels the most annoying part–parking. So, if we do go to the beach, we go after the lifeguards and parking attendants leave.
Luckily, Falmouth and the surrounding area has tons of other fun things to do with kids, besides going to the beach.