Never actually needed to stay in DC (I live like 10 mins away), but bubba gives good advice. Get a place thats near a metro stop. The metro makes things a lot easier. You really want to avoid driving in the city if you can. Its very annoying; bicyclists, peds, taxis that follow their own made up traffic laws, and people that use their magic 'park anywhere' button (hazard lights...).
Heres a map of the metro system to help you make a choice:
There is actually a stop at Reagan. Arlington Cemetery is on the blue line, and Reagan is on the Yellow line. So you'll probably want to find a hotel that is near a blue or yellow line stop (or a stop thats close to the "cluster" you want to hang out in)
Also, give me a holler if you need anything or if you guys want to grab lunch or something!