Be sure if you ride on the Colonia Parkway, it's kind of rough pavement.
You didn't say what type of bike you ride, but I would guess a road bike would be harsh. We(my family) took our MTB's up there last year and peddled about 14 miles of it. It was nice.
Williamsburg is great for bicycling, they have alot of bike lanes(not paths like in VA-Beach, which are mostly for cruisers)
Anyhow have a great time.
If you need any last minute items the LBS is Bike Beat, never been there, but they have a commercial on OLN during Thursday Night Bike night.
http://bikebeatonline.com/
I hope you have fun, take pics for us.
BTW, a good route is to take the Ferry across and ride over in Surry, VA Lots of country roads and Good Pavement.