Any recommendations on areas to do a quick (4 day?) vacation with a 2 year old within a few hours of Boston? Our idea is some kind of cabin on a lake, where we can play in the water, maybe some light boating, and generally relax a little and enjoy the fresh air. Nightlife not required as we will have to be home by 7:30 and I'm pregnant

No Cape Cod as we visit family there anyway. Not sure what regions to focus on and we'd like to go in the next couple of months (so I'll prob end up looking at last minute options anyway). Thanks!