What a coincidence! We just got back from a few days in a lake-side cabin near Machias, Maine. Had a wonderful time. Acadia National Park is nearby, and so are a lot of little towns on the coast just across the water from Canada.
We live about 50 miles from Boston, over in New Hampshire. One "must see" for anyone interested in American history is the John Adams house. You can get there easily on the "T." It's almost exactly as it was when he lived there. Filled with priceless antiques and historical objects and documents. His personal library, with its original contents, is right next door. Fascinating!
I can also highly recommend the Fine Arts Museum, the Museum of Natural History, the Science Museum, and the Isabella Gardner Art Museum (a little off-beat and quirky, but well worth the visit). You won't be disappointed. And whatever your political persuasion, the JFK Presidential Library and Museum is very interesting and informative from a historical perspective.
Have a great vacation! Don't forget to post some pictures when you get back...