Bar Harbor/Acadia is definitely a must see. If you are into history at all, Williamsburg, VA, and Gettysburg, PA should be on your list. Boston has much to see and do but the RV would have to be left at a campground. Parking the truck would be difficult, but not undoable. You don't say what time of year you'd be traveling, but keep in mind that with just a few exceptions campgrounds up here don't open until April and close by Columbus Day. Holiday weekends and peak summer season (end of June through end of August) book up very quickly. You should give serious consideration to reservations during those time frames.