We went the second week of September. The weather was great and not a lot of people. The only thing you need to watch for is home school days because they come in groups.
We stayed at American Heritage CG, it was the start of their winter rates, which are a little cheaper. Great place, very clean and trash pickup at your site everyday. It is close to Colonial Williamsburg. From the CG we went down Route 60 to the Colonial Parkway. There are quite a few restaurants and shopping areas along the way.
We did the 7 day ticket, it was nice because we could mix up our visits to all three areas depending on the weather. Buy your tickets online. At Colonial Williamsburg you go to a special desk to get your pass and the line was non-existent. The non ticket holders had lines. Also there is not much if any discount I could find on the 7 day ticket.