I have been there several times and friendly older gentleman in the front will not force you to donate. It's up to you. Although the donations pay for his time and caretaking duties. It's well worth the $10 and the kids will have lots of fun.
Trip Advisor says they're now asking for a $10 donation per person, up from $5. That being said, I wouldn't expect to donate for the children but I am ASSUMING that. It's a nice little museum though.
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