Have you thought about Crystal City Va. Major Hotels such as Sheraton, Marriott, Quality Inn are right at the airport and underground Metro links. The undergruond links will take you to any part of the Smithsonians and a shopping mall. I stayed at the Quality Inn, when I went to do some ancestry search at the National archives. I loved the transportation system. Very clean and safe. I'm not sure if the Quality Inn is still the name since hotels buy out each other but the other hotels were very close in walking distance to the metro underground subway. And the prices may be cheaper.