the network for radical unschooling families
We don't live in Boston but we're about an hour away in Worcester. We have a membership to the Ecotarium here in Worcester, which is reciprocal with the Boston Children's Museum. We try to get in at least a handful of times a year...I believe that they have some free nights as well. It's a nice spot, right near the water. so watching the boats is fun, too. I'd say that renting near MIT would be a great location for lots of other stuff, too. Ther are also loads of free things happening in the summer months...free concerts, etc. Maybe someone from closer to Boston can be more specific.
HTH! And best of luck with your move!