Membership has its privileges. If you think that you might go more than once in a year, you HAVE to be a member. I bought mine almost two months ago and we have already been four times. They have special members events.
It's smaller than other childrens museums in other cities, but my 4 and 8 year old LOVE this place. Two hours and I am still dragging them out of there. I think one day we spent 4 hours there.