Acadia depends on how much you want to hike and what else you want to do. You can technically "see" the park in a day, but if you want to "enjoy" it I'd base the rest on what you might what to do in the park, such as biking, hiking, playing at Sand Beach, taking a carriage or horse back ride, etc. You will also want to spend time in Bar Harbor just puttering around. Take a sail or whale watch out into Frenchman Bay. If the girls like shopping stops in Kittery and/or Freeport are a must. You can spend quite a bit of time in either. For an anomaly visit the Desert of Maine, which is right outside Freeport. In NH you can go up to the White Mountains. The Flume Gorge is an interesting site and there are a bunch of small amusement type parks. Clark's Trading Post with the trained bears is a must. However, keep in mind it's 250 miles between there and Bar Harbor. Vermont has the Quechee Gorge and with girls that age the Vermont Teddy Bear factor in Shelburne. It's hard to remember all that's available and pick favorites.
