Dutch Wonderland in Lancaster, PA. Its an amuzement park geared to 8 and under set. We have taken our 5yo every year since he was 2. Great family friendly destination too.

Outdoor or indoor entertainment options? My 4 yo thinks Baltimore is heaven on earth due to Port Discovery and the Maryland Science Center, and he hasn't even seen the Aquarium yet. We don't stay overnight, though. 2-hour drive is pretty restrictive unless you're looking for outdoorsy stuff. (Would camping work? Many options there, but it's getting kinda chilly.)

Any ideas? I'm not very familiar with the area so any tips would be appreciated