Im located in Boston, MA and am ever to get the ball rolling with ~fall activities~ (think apple picking, breweries, thrifting, hikes with beautiful views, cute north shore towns, etc.)
Davis Farmland has a fun fall activity area. It starts in October and you can go to a cornmaze, lots of stuff for kids, and also BBQ. We also like Tougas Farm in Northboro, MA it has pumpkin and apple picking but also animals and lots of playground equipment for the kids.
You've got about one more month of whale watching season and you don't want to miss it! Groupon has some great rates, but also the aquarium does combo tickets for admission and a whale watching trip