We want to go on a vacation with my in laws this summer, somewhere with a four hour drive of DC/Baltimore. Last year, we went to Lancaster PA and it was great.... my kids loved the farms, the train stuff, buggy rides, etc...

My kids are not interested in roller coasters, bumper cars, that sort of thing....we're also not really interested in a beach type vacation... they can sit on the beach for 1/2 hour, then get bored

Are there any other vacation destinations in the mid-atlantic region that are not beach or amusement park based for us to consider?