There are some great museums and cultural opportunities there. I'm firmly of the opinion that everybody ought to spend two, maybe three weeks in DC. Go to the Smithsonian, the monuments, see the Capitol and White House...then turn in any direction and run, don't walk, away.
I'm with Dave on this one. I'm a museum nerd and could probably spend a week at just the Smithsonian. Plus, I hear there's an amazing aviation museum across the river in VA. Needless to say, I drive my kids NUTS on vacations where there are cool history sites and/or museums. After three or four hours at the same place, they get antsy. Ridiculous.
I don't know, I like technology, and seeing some of the science stuff might be cool, as in the Smithsonian. But honestly, I just can't get into museums all that much. I mean, I just got back from AZ, took The Boy to see the Grand Canyon and visited my grandparents in Mayer, outside of Prescott. We had a free day and the wife and my mother convinced us to go to some museum there in Prescott, and I was honestly pretty bored. I know about the Old West, about early pioneer life and such, but when I'm on vacation, I just don't find museums to be something on which I honestly want to spend what little time I have there. I'd rather be DOING something... you know, boating, fishing, swimming in an ocean, even just lying on a beach and enjoying the sun I find more fun. Hell, I was at this museum where they've taken all the time to restore everything, recreate scenes of old pioneer living - women washing clothes, coyboys and Indians facing off, fire brigades pulling their carts down the street, even some of ancient hunters fighting off wolves - and I just think, "Really? This isn't what I'd spend my free time doing, making museum exhibits." Of course, I'm sure some of them were professionally made, or all of them, so those people got paid, but it just doesn't tickle my fancy as a worthwhile use of half a day of my rare time off.
Diff'rent strokes for diff'rent folks and all, I know that. I just... don't get it.
I don't think you'll ever convince me to go to DC. I realize all the stuff there is important in the history of our country and all, but no way in hail I want to bother with that place. Hope you enjoy your time, though.