I have 3 suggestions.
Cape Cod -- I think you would love the "Old King's Highway" namely Route 6A on the Cape. It goes along the northern side of the upper arm of the Cape. It's historic and beautiful. You could stop at several of the towns along the way, or beaches. I myself find Sandwich boring but the areas farther east seem more interesting. Barnstable is pretty,. You can keep heading farther up the Cape, too, to Eastham or Chatham. Chatham is extremely pretty and you could visit the historic lighthouse and walk around the town center -- my favorite all-around town on the Cape.
2. North Shore of Massachusetts, including Marblehead and Rockport. If you do this, try to drive up to the northern tip of Cape Ann, which is very beautiful. If I remember right there is a wonderful park there which is mainly quarry land, and you can explore it and walk down paths to the water in several places. (I'm sorry, I have forgotten the name of this park) Most of the towns in this area are pretty and worth visiting. I think Marblehead is very rewarding and fun to walk around. Rockport has a beautiful harbor area with lots of shops and restaurants. Manchester is also very pretty with a beautiful harbor . . . . You can get to this general area in an hour or less from Boston.
One other spot north of Boston that is also beautiful, is the town of Newburyport with nearby Plum Island.
3. Concord and Lexington, west of Boston. If you do this, don't skip visiting the Old North Bridge. It's very historic, nicely presented, and in a beautiful natural setting. You will probably see canoers or kayakers on the river. Walk around either Concord or Lexington Center. Both are really very nice. There are some great old cemetaries in Concord. Both towns have lots of colonial architecture. You could also include Walden Pond in this trip, although you'd need a car to get there.
As for foliage, it's starting to happen a little early this year. The weather people say it's because there is a slight drought around here. So, you should see some fall foliage, and that would be a nearly ideal time to visit. Remember it will be crowded since that's a big tourist time. If you need hotels, I'd reserve them now.