My family has gone to Williamsburg for the past two years and what we've done is get the park jumper pass for Williamsburg, Water Country and Busch Gardens. We got four - myself, my wife and two kids. It allows you to go to any of those three parks any number of times each day. Also, one of the jumper passes is a gold one, which allows us to park for free. IIRC, Busch Gardens and Water Country charge you $10 to park. And I believe the gold pass gives you a discount on food and stuff.
You can get the passes at the Williamsburg visitors center.
Also, don't eat in Williamsburg. They'll charge you an arm and a leg for drinks, snacks and meals. Pack a small bag with drinks and snack and be sure to ride the bus.
Any more questions, just ask. Later.
Matthew