I've lived in DC/Arlington for my whole my life (other than going to college at ISU and living in Syracuse for two years), so I can help you out. It sounds like you have most of the museums and landmarks already booked and taken care of, so that's good. If you're looking for a very good place to eat, try Oyamel. It's Spanish tapas and is absolutely delicious, but a little pricy. Go check out Navy Yard and see a Nationals game there if you're into the MLB (try to see Scherzer pitch since he's a freak). U Street area is a lot of fun at night if you're into going out at night. DC is a very culturally diverse city, so any kind of food you can think of, there's a good restaurant for it. If there's a specific type of food you're into, just ask and I can probably give you a decent recommendation. Be prepared to spend some money as DC is very expensive (similar cost to NYC). There are also some very good music venues in DC. See what's playing at The Anthem, 9:30 Club, Echostage, or The Fillmore Silver Spring while you're in town visiting as a lot of good music acts come through DC. Have fun in DC!