I really don't think it's a good idea to try and leave your luggage at the UA lounge; too many bad things can occur.
I'm going to move your thread over to the Washington D.C. Forum so the members there can help with your questions. You may also want to take a look at the following threads:
http://www.flyertalk.com/forum/washi...ities-iad.html
http://www.flyertalk.com/forum/washi...useum-iad.html
Safe travels,
FlyinHawaiian, Co-Moderator
United Mileage Plus Forum