Great time of year to visit us. Weather is nice, and not as jammed with school groups as it is in spring.

More info on events that might be on during your visit here:

http://www.washington.org

I wouldn't recommend this on your first trip to DC, but staying in Reston and having a car, you could do some scenic drives in Virginia and visit some wineries (but you should definitely head into downtown DC if it's your first visit).

http://www.virginiawines.org/