I somehow had to go to DC 3 times when I was a kid. My only lasting memories are the Air and Space museum (fucken sick) and some nigger trying to knock my old mans Nikon off his shoulder.
In more recent news my kid went on a school(I paid $300.00) "sponsored" trip last year and he bitched about all the walking/point droning on and assorted frivolousness
that most 11 yr olds would perceive a "tour" to be.

Astronauts, The Declaration, and the White House are cool.
Anything else and you might want to plan some roller coaster/pool time in between.