Definitely Williamsburg, but also Jamestown and Yorktown, which aren't far. It's not the right time for you for the special homeschool discount rates, but if you don't have a ton of time, you can just walk around Colonial Williamsburg and observe the architecture and interpreters' dress and such. You just need to buy tickets if you want to go in the buildings (unless things have changed in the past couple of years). There are two Jamestown sites; one has the site of the original settlement and a collection of artifacts, and the other has two recreated villages (English and Powhatan), ships, and an amazing gallery of artifacts. There is also a Yorktown Visitor Center, with an army camp, colonial farm, and galleries; you can also visit the Yorktown Battlefield, though we have not personally been there. We thought all of the sites were neat, but with limited time, especially in the winter, I'd opt for Williamsburg and/or the Jamestown Settlement (the one with the recreated villages and galleries). More info: http://www.historyisfun.org/Jamestown-Settlement.htm Also, history.org (Williamsburg), historicjamestowne.org, and nps.gov/york.
In southern Maryland, Historic St. Mary's City. http://www.stmaryscity.org/ Other southern MD sites here: http://somd.com/culture/historicsites/
In northern Maryland, colonial Annapolis.
In Pennsylvania, outside of Philadelphia is Valley Forge (though it's very near King of Prussia's huge mall, so around Christmas is likely to be very crowded). I've not been here, but this looks cool (and not far from Philly): http://explorepahistory.com/attraction.php?id=1748 More in PA: http://explorepahistory.com/story.php?storyId=20
I know nothing about New York and New Jersey, sorry. :) If you have the time, Plimoth Plantation could be a (long) day trip. And of course, there's Boston, but that is also a longer trip.
Oh, and I just found this site too while looking: http://usparks.about.com/od/revwarsitesnatl/Revolutionary_War_Sites_National_Parks.htm
(Sorry, that got long. History is kind of one of our family's "things," and we've been privileged to work at and/or live near a lot of historic places up and down the east coast.)