You may want to check rates at the Loew's L'Enfant Plaza. They are centrally located to the mall and major road in/out of DC. The hotel is nice enough - modern. Very close to the Smithsonian and there is a Metro station under the hotel for access to the rest of the DC area without going aboveground or taking the MCS.
The Spy Museum is a very "happening" museum right now. Get tickets in advance. If you are coming in January and like aviation, the Smithsonian will have their new annex at Dulles Airport open by then. They are running a shuttle bus from the Air and Space Museum out there or you could drive. It opens mid-December.