We went once last year - at Labor Day. We went outside first and never even went inside.
This time the first outdoor entrance was closed, so we had to walk through the rest of the museum. The girls loved it. They liked playing in the space capsule, but Madeleine was afraid of the moon landing setup and astronauts. They had high school students doing face painting. Lily would have spent all day in their "Play and Learn" area if I would have let her. We had to DRAG them out so we could make our 11:30 train ride.
We also did a quick run through the butterfly house and the farmyard. The girls were getting worn out in the play area, so we were out a little after noon. Hopefully next time they'll believe us when we tell them that the museum is fun and we should get ready earlier :)