Give
Madigan's a try. 210 Mill Street in Occoquan - 5 minutes from where you are. The menu is pretty good and its not too pricey. They have bands on some nights. Good food and good fun. I could go on forever about places in DC but I think its best to pick something close to where she lives for a first date.
If you tell me what part of DC your date is from I can give you some ideas close to where she lives. If she is from Bethesda, for example, I wouldn't drag her to Occoquan. At least until the 2nd date.