The Museum of Flight is a jewel of a destination in Seattle. There are world class space, commercial and military aviation exhibits - with a newly rebuilt jet park where you can walk into famous planes like Air Force One and the Concorde. The Museum operates a number of STEM programs throughout the year for kids, and hosts a wide range of talks and presentations. The museum is located next to Boeing Field and has ample parking (although it gets super crowded around Blue Angel time in the summer). It maintains one of the best gift shops in the city, and will keep you busy for at least 2 hours. Since there's a lot of walking, you'll want to bring a stroller for the littlest ones.