The College Park Aviation Museum is a hands-on museum for learning about the history and mechanics of aviation. Lots of programs for families and kids such as the Peter Pan Club is the College Park Aviation Museum's pre-school learning club (2nd and 4th Thursdays of every month from 10:30am-11:30am. Afternoon Aviators is a weekly activities series for children ages five and up (every Friday from 2pm to 4:30pm and free with regular museum admission).
This was one of my boys favorite places we visited while in the D.C. area. It was not crowded at all when we visited. The displays were high quality. They especially enjoyed the multiple simulators you could try out including one for the Wright Flyer! A lot of great aviation history as they bill themselves as the Cradle of Aviation. Some planes you can actually sit in. Don't miss it if you have aviation fanatics in your family.