Went there once with the Boy Scouts, back in '88 I think it was...was mostly interested in patch-trading at the time, so didn't spend much time actually looking at the exhibits. I kick myself now...although I do that a lot, thinking back to all the time I've wasted as a kid. Heh. One of these days, I'm gonna get myself back to Washington DC!
One thing you might consider, Harrison, is taking a tripod or monopod along with you. You don't have to open the tripod legs out all the way, so you can have the small footprint that a monopod offers, but with three points of contact for the better stability that the tripod offers. This way you can leave the shutter open for longer periods of time, giving yourself more light and sharper images. Trying to hand-hold a zoom lens indoors is difficult, at best. Great pics overall, though!