deCordova Museum and Sculpture Park

A great place to go with kids to expose them to art from an early age.  The sculpture park is perfect for your active little ones who want to run and discover and enjoy the outdoors.  The sculpture park encompasses about 35 acres of land and is surrounded by trees.  Some sculptures are interactive and some integrate into the natural surroundings.  The deCordova also can be accessed with a Minuteman Library pass so that admission is free.  Additionally, in the summer they host yoga sessions for both adults and children on the weekends, as well as artist talks, and sculpture garden tours.  The museum also has workshops and is home to a nursery school.  The interior of the museum is host to changing contemporary art exhibitions.
The grounds are perfect for picnicking and enjoying a full day of exploring.
One last family-friendly point is that the restrooms all have changing tables!

deCordova Link

Museum of Science

One of Boston's best resources and venues is the Museum of Science in Cambridge.  The museum offers a wealth of information and exhibits, most of which are interactive.  It provides information and entertainment for primarily school age children through teenagers and adults, but also has a small area for the younger preschool/toddler age kids.  There are presentations that run everyday that are free after the admission fee is paid, as well as an Omni Show, which is an additional cost.  The presentations vary from animals to weather and the ever popular electricity show, but are all engaging and given by knowledgeable presenters.  Much of the museum staff are volunteers, many of whom have been there for years and know the museum inside and out.
Exhibits cover topics from optics, to health, force and motion, rocks and minerals, to local issues like the Big Dig.  There is a Butterfly Garden and Planetarium in addition to the other exhibits.  The museum has a cafeteria and a gift shop.  During the school year the museum is often overrun with field trips, so moving through it with younger kids can be tricky.  The is enough space and if it you time it correctly you can work around the large groups.

The museum is also located on the Charles River and is convenient by public transportation or the highway.  It can be rented out as a venue for private events also, and if you are an educator, offers a discount and has an educator's library. 

Museum of Science