Seconding, (thirding?, fourthing?) Baltimore/DC. I am a college student in Maryland right now, and the Smithsonian are fantastic for me, and I can go to them whenever I want! Totally free and awesome. American History and Natural History are my favorites, and the Air and Space is not to be missed. If the Air and Space isn't enough, you can go to Dullas to get into the second part of the museum (overflow, they have a space shuttle there!
) for a small fee, I can't remember what.
My parents were very big on instilling into me an appreciation for our nation's history. It's possible you could find kid-oriented things to do, you can look at the monuments if that's your thing, etc.
Also in Baltimore you have the Orioles. Camden Yards is beautiful, though if you go to an O's game don't expect to win, we haven't exactly had a winning team since I was in elementary school...
The Baltimore Aquarium is I'm pretty sure hands-down one of the absolute best in the country. Beautiful exhibits, a rainforest in the roof, sharks, dolphin shows, huge walk through coral reef tanks... AND there is the MD Science Center, which is full of hands on science exhibits, Newton, your body, outer space, and always really good travelling exhibits.
And in Virginia as mentioned we have the historic triangle, Williamsburg, Jamestown, and Yorktown, the beginning and end of the U.S. as a colony all within minutes. Williamsburg has really blossomed as an attraction over the last few years, all kinds of reenactments going on there now. Also in VA you might want to look into Lurray Caverns for something totally different.
It's funny, I live near all of this so it's no biggie, but if you guys haven't been down here before, you really should give it a try! Let me know if you have any questions