You will not have any issues finding things of interest. You could easily spend the entire visit in the Smithsonian museums including Air and Space and National History Museums. Other museums include the Hirshhorn, National Gallery of Art, and specialized national museums for women's art, Asian art, African American Art and many others. Don't forget the Washington and Lincoln Monuments. There is even a substantially size zoo. Do a little research and decide how to pare down all of the choices to what you can handle in that limited time period. Wear good shoes.