I don't know why it took me so long to get there, but my daughter and I finally made it to the Discovery Museums in Acton, MA. And yes, I am kicking myself for not going sooner because my daughter had the best time EVAH.
In case you've never been, the Discovery Museums (from their website) "are two separate but complementary museums filled with exciting, interactive exhibits for children of all ages using focused spaces and hands-on activities inviting exploration and discovery. "
The Children's Discovery Museum, housed in a converted Victorian, is in fact room after room of these interactive learning exhibits, each with its own theme. For example: The Safari Room (complete with "wild" animals of the stuffed variety and climbing nets), The Water Room (waterproof smocks are provided so kids can splash in the large tub with abandon), The Ball Room (think of the game mousetrap when it's completed and that's a bit like the Ball Room), and my daughter's favorite, Bessie's Play Diner (booths with jukeboxes, a play kitchen with a diner's counter, play food and cookware).
The entire third floor is the S.S. Discover (a "nautical adventure", Ahoy!). Oh, and there's a Rainbow Room as well, which my daughter enjoyed because it had a slide, but is not at all like this place. Bummer for me, bonus for my kid.
I was there with my in-laws, my husband's nephews (ages 4 and 8) and my daughter (not quite 2 and 1/2). The Children's Discovery Museum was perfect for the 2 and 4 year old but it was far too young for an 8 year old boy. He would have been better off at the Science Discovery Museum, but since this was our first visit we didn't know much about it and didn't leave enough time to visit it.
A word of caution if you have kids that different in age: You have to pay for the Children's Museum and the Science Museum separately. And you need to leave a lot of time to do both (we spent about 2 and 1/2 hours in the Children's Museum). A better bet would be if one parent could go with one kid to one museum and the other parent go with the other kid. That would save time and greatly cut down on any over-stimulated tantrums.
If you're thinking of going at a time that will run you into lunch, there is no indoor eating facility so you'll have to go out to get a meal or bring your own (there are a few tables outside for eating al fresco on nice days) but your hand stamp grants you access to whichever museum you paid for for the entire day.
(There's a McDonald's right down the street. Just a heads up.)
I have a feeling we'll be going back very soon. The Discovery Museums are incredibly easy to get to from both the Boston area and 495. If this directionally challenged woman can get there, anyone can. If we lived a bit closer I'd purchase a family Membership, but even though it was easy to get to from my home outside of Worcester it still took about 40 minutes to get there. Including one stop at Dunkin Donuts. Because, really, if a place is that fascinating for infants, toddlers and preschoolers then you can imagine a parent needs a little caffeine before going in.