We will be at BG on 8/28 ourselves! We

BG and have a season's pass (actually I guess it's like yours - for all of the BG & SW parks). The last weekend of the month is Wild Days! This year - Julie Scardina of Jack Hanna's group will be there - they bring all kinds of animals to the park and there are special shows and interaction opportunities. This is held Sat/Sun - 8/28 & 8/29.
Something we haven't done yet - but want to - is to visit the Yankee Candle Factory - it's a Flagship store and evidently has tons of family things to do. I know there is a candy shop, Christmas shop, make your own candles at Wax Works, etc. I found this on the website - ** Rated as one of the top Williamsburg Destinations by Disney Family Travel **... so something to check out.
If you like seafood - one of our favorites is Captain George's - it's an all you can eat seafood buffet... we make a point to go at least once a year!
http://www.captaingeorges.com/SetYourCourse.aspx?loc=1 (Not cheap - but AYCE crab legs seldom are!)
I always Priceline a room and usually get something nice for between $50-$70. Beware - there are a lot of "Mom and Pop" motels that are not so nice.
Hope you and your family have a great time in Williamsburg!