You can try posting on Fodors.com forums, they are a pretty good source of information. To get the most out of your inquiries there (or here, for that matter), it's good to at least include who is in your party (adults, children including ages), any special needs or interests, where you are staying if you know, or parameters for where you'd like to stay (budget, proximity to stuff) if you don't, whether you will have a car, etc.
Also, note that Williamsburg is about 3 hours' drive from DC. Depending on how long your visit is and how you are travelling and such, you may want to reconsider including Williamsburg in this trip. If you do want to include a side trip, other possibilities include Gettysburg or Charlottesville.