We went there this weekend (8/10/2013) and even though it was a Saturday there weren't a lot of buildings open like there was supposed to be. Maybe it was because it wasn't a special weekend, but I couldn't imagine paying the full price ($21 for adults) just to go into two or three buildings. My husband is active duty military, so we got in for free. I just thought there would be more open/going on that really was.
On a side note: you should know that this place is NOT stroller or wheel chair friendly. We didn't learn thin until AFTER we arrived at the visitor center and parked. Navigating through the streets was a nightmare with a stroller.
We'll probably go back in the future, but only when there's something special going on.