Overall, recommended: mainly for the seasonal shows, which were fantastic! Drawback: a few of the rides were closed until evening because they were turned into haunted houses, hence limiting your fun if you do not want to experience the Haunted Houses.
We went to Busch Gardens Williamsburg on October 1, 2011 and found the park decorated for a darker- version of Halloween. We entered the park at opening and stayed for the daylight hours. My family was really liked the seasonal Halloween Show called ‘Monster Stomp Revamped’- My son really liked the Skeleton Dance. The whole show was impressive to watch, and very crowded so get there early! I personally enjoyed the Fiends Show in Germany’s Hofbrauhaus. I would recommend eating before or after the show- not during because the show will hold you attention and your food will get cold. (I was worried about this and ate beforehand, but more because of the ‘ick -factor.’) Just so you know- the show is not gross. The Fiends show is Dr. Frankenstein meets Rock Opera. We also watched the outdoor Jack is Back Show and it pales in comparison to the other two shows. The park has disclaimers about having your children watch the shows, but we found that they were all acceptable for our 9 year old son. Some were heavily laden with scantily clad women dancing around, but its no worse that what is on the TV.
We opted not to stay for the Haunted Houses and Scare Fest of characters that jump out and try to scare you. This element opens at 6 PM. There was plenty to do during daylight hours to experience a family-friendly, semi-spooky Busch Gardens Halloween. Please note, the park seemed to get a huge influx of people around 5-6 PM.