Hirshhorn Museum

Carved horses and an accessible chariot for riders who can't climb on, right between the museums.

Landmark planes and spacecraft overhead, and a gallery on how flight works with a plane kids can sit in.

Hotel a few blocks from the Mall museums, with a kids' corner of arcade games and foosball.

Galleries inside and a sculpture garden outside, so when kids are done with paintings there is room to walk among the big pieces.

Dinosaur skeletons, animal halls, minerals and ocean displays under one roof, so each kid finds a room they want to stay in.

The founding documents themselves, with interactive displays that explain them. The line can run long, so go early.