Besides the good walking shows make sure you bring a bag that is easily searched by security. Every museum and most buildings here search bags and will ask for ID.

It is also supposed to be in the high 80's low 90's next week, so wear plenty of sunscreen (as someone who burns very easily I can attest it is not "fun").

I would also recommend the Holocaust Museum, I can not say that you will enjoy it, but you will certainly be moved by it.

If you enjoy art work, the National Art Gallery is wonderful. Take a look at the Smithsonian website before you come because they will give you a very good idea of what is showing at each of the sites (there are 11 different sites).

The Spy Museum is also alot of fun (very interactive) and the Postal Museum is entertaining and quircky.

If you want to get together let me know and I will PM you my phone number.