Homemade ice cream is really popular out on the Cape, and likely with your kids too! Here is a link to a ton of ice cream places on Cape Cod (including ones in Chatham): http://tiny.cc/XxXMh

On the more casual side of seafood restaurants, you should definitely check out Chatham Squire. The local steamers are delicious!

Also in Chatham are Vinings Bistro, The Impudent Oyster, and the Roo Bar. Of these, I think Roo Bar is better for including the kids. Vinings and Impudent Oyster may be more fun without the kids.

Here is a link to restaurant recommendations by Town (including Chatham): http://tiny.cc/Yuhvi

Mini-golf is another popular activity on the Cape in the summer, we have a great list on CapeGuide.com of mini-golf spots, by town: http://tiny.cc/kShAn

If you're feeling really adventurous, you could take a day trip over to Martha's Vineyard. The ferries run regularly throughout the day, leaving out of Hyannis and Woods Hole.

Have a wonderful vacation on Cape Cod!

The main restaurant at the Wequasset is really wonderful for a little dressier dinner.