You picked a bad time of year for outdoor activities. We're in the dead of winter, which means anything outdoors is probably shut down for now. You can go hiking in any of a number of spots, but those might be kinda rough when it's so cold out.

That said, there's still a lot of fun stuff to do in Mass. There's the Minute Man National Historical Park (a series of small museums covering the opening battles of the Revolutionary War) and Boston's Freedom Trail if you like to walk. For more indoor activities, there's the New England Aquarium, the Boston Tea Party Museum, the USS Constitution, Bunker Hill Monument (it's not outdoors but climbing to the top is a bit of a workout!), Hammond Castle, the Eustis Estate, the Witch House at Salem (call them up for times, as they're open less often during the winter), the Salem Witch Museum, the Isabella Stewart Gardener Museum, the Museum of Fine Arts, the Museum of Science (lots of museums in Massachusetts!), and the JFK Presidential Library, among other options.