I live 200 miles away and have been traveling to CW for 20 years. I have been known to go down and back in the same day just to see some special programming that might be going on at certain times of year. For those planning a trip, the programming is scaled back between New Years and Easter. (The last two years it has shut down for the month of January, although the town can still be walked through.) Spring break is when things start to pick up, full programming returns, and the crowds increase. It's a great time to visit with smaller children because so many baby animals are being born. Summer is in full swing and the crowds are larger. It's a great place to spend 4th of July, just by virtue of the nature and history of the place and the patriotic programming that day. Autumn is a WONDERFUL time, my FAVORITE time of year to go - the weather is great, the foliage is beautiful, full programming is still going on. In addition to some on-and-off events, like George Washington's pre-Yorktown encampment taking over the town, they do a VERY nice Veterans Day event. And then the Christmas season kicks off with Grand Illumination the first weekend and beautiful decorations (albeit c. 1930s, hearkening back to when the Restoration took place) and Christmastide programming of all kinds, including music, dance and character-driven ones. Currently they have interpreters representing George Washington, Thomas Jefferson (young and old), Patrick Henry, George Wythe, George Mason, James Madison, the Marquis de Lafayette and Martha Washington, as well as numerous other named townsfolk of the era, and you won't find historians any more knowledgeable or immersed in their subjects that those playing the roles. The trades range from candle and shoe making to coopers (barrel makers) printers, furniture makers and even brick and beer makers at certain times of year. And the DeWitt-Wallace Museum is world class, with an extremely impressive collection of folk art, much of which belonged to Abby Aldrich Rockefeller.
Unfortunately, it has become a common complaint in recent years that CW is pricing itself out of the reach of many families, even while it has added more activities for children, such as the archeological dig during the summer time. It is true that passes and food and souvenirs can add up (although it's still a cheaper option than Disney World or even the two amusement parks that are nearby.) I recommend packing lunches or eating off-site. There are few options in Merchant's Square, a few blocks' walking distance outside the Historic Area, that are easier on the wallet of families with children - notably "Retros" on Prince George Street. But they will not find a better opportunity anywhere to delve into history as deeply or gain as great an appreciation for their Founding as they will in Williamsburg, so if it is important to you that your children develop that sense of pride, it's worth the investment. CW doesn't sugar coat things. They tell the story "warts and all" including colonial slavery and interactions with regional tribes that both sides courted for frontier warfare during the Revolution. So they won't come away with only one side of the story. And the interpreters LIVE for the opportunity to interact with children and young people. They all recognize that future is theirs.