I love visiting Harpers Ferry. If your an adventurer, they have several outfitters that will take you canoeing, kayaking, whitewater kayaking, mtn biking, canal biking and/or rock climbing.
Parking is limited in the lower historic area. Park at the National Historic Park and take the free shuttle to the downtown and back. But, in busy season be prepared for lines and waits unless you go in off-peak hours.