Out in western Fairfax County (not too far from the Smithsonian Air and Space Museum in Chantilly) is Sully Historic Site. Throughout the year the property offers many family-friendly events and Christmas is no exception.
During the days (from Dec. 3 to Dec. 28) visitors can experience an 18th century Christmas holiday. The Sully home is decorated Victorian style and visitors will "relive" the memories of a visitor to the home in 1885.
When we went to the Victorian and WWII candlelight tours, we did register ahead of time (I know reservations are recommended as we had a set time slot, not sure if they are required).
More information can be found on Sully Historic Site's website.