Help for the summer!

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I am a nanny of a 3yr old (will turn 4 in may) and a 2yr old (will turn 3 in july). I am trying to find some different, fun, somewhat educationaly places to go with them this summer. The area would be from about king of prussia, pa to allentown, pa areas...they are very well behaved children, so im not afraid to take them places. we have some parks around us that we will go to and some other places like mini golfing and the one movie place has free movies every wednesday that we can do to... but i wanted to know if anyone else had any suggestions of what we could do...thanks in advance! :)