Central or Upper Bucks county fits your list to a T. Almost midway to NYC and Philly. Shortish drives to mountainous regions in PA and NY. Close to Jersey beach and even DE/MD. 5ish to MA. Towns like New Hope and Doylestown are close. And state parks abound with access to short hikes, camping, and kayaking on the rivers.

Edit: as others have noted you may be priced out depending on where in bucks you look. Lehigh valley is an option too.