I don't know too much about Framingham, but I think there is still a playground on Route 27 near Route 30.
If you want to drive west 2 towns to Westboro, there are a couple of options. Take Route 9 West past 495 and then take Route 30 West (there's a Chateau Restaurant at the exit - go slow because it's a tight turn.) There is a McDonald's right there that has a play area but you may not want to get into the McDonald's habit.
On Route 30 on the left about 1/4 mile from the McDonald's is the Hastings Elementary School with a play area - can't use it during school hours but it's available weekends and holidays. A little further down on the left you will see a sign for the Senior Center - take that left and go all the way to the end of the road - there is a playground at the ball fields.
Continue down Route 30 West to the rotary and intersection with Route 135. Go 3/4 of the way around the rotary and take Route 135 EAST about 1/2 mile. You will see a sign for Harvey's Farm on the left. It is a garden center but they have some penned farm animals (goats, pig, various fowl, etc.) and they sell animal feed very cheaply in the store. There are rabbits in various hutches too. From the covered bridge, you can look over into the pond, and there are lots of ducks that come looking for food. There are catfish on the bottom who swim up and grab everything the ducks don't catch, so it can be fun to look at.
You can also go to Tougas Farm in Northboro - you can Google them, or take Route 9 West past the Route 30 exit I mentioned above, and take Route 135 West to the end. (You'll past a playground on the right, Ellsworth-McAfee, and another on the left just before Route 20.) Go left at the light onto Route 20, then bear right at the next light onto Church Street. Take Church a couple of miles, all the way past 290, and then follow signs for Tougas. They have apple-picking, hay rides, farm animals, pumpkin picking, and so on.
Another fun trip is Southwick's Zoo in Mendon - get info on line. It isn't what I would call cheap, but it's a great resource and there's something for kids of all ages. Same with the Roger Williams Park Zoo in Providence, which isn't really all that far from you. There is a huge park open to the public for free, and there is a fee for the zoo. It's a spectacular zoo. Take a stoller to this and to Southwick's.
There is a Children's Discovery Museum in Acton - again, you can Google them for directions. There are 2 buildings, and one is a science museum for older kids, but the other is great for kids 2-7. It's a converted house, and each room has a different hands-on theme (water play/bubbles, a ship, animals of the Serengeti, an old-style diner, balls & ramps) and so on. I think it's only about $7 which isn't awful. Great rainy day activity as it is all indoors.
Check the Danforth Museum in Framingham - they have kids' activities but I'm not sure of the ages.
Local libraries also have passes for area museums - they are free but sometimes you have to reserve. They have passes for the Boston Children's Museum, the Museum of Science, the N.E. Aquarium, the Ecotarium (Worcester), and many more. Your library would also be a great source of info on other local areas, and maybe on playgroups too. Sometimes other parents put notices on the bulletin boards there.
If you find a place you really like, consider taking out a year-long family membership. Then you can go as often as you like, and if your son gets tired after 90 minutes, you don't feel like you've wasted all that money for admission and you have to stay for 5 hours to make it worthwhile.
Also Sudbury Valley Trustees maintains a number of local natural area properties which are open to the public at no charge. Depending on which ones you choose, there may be ponds and streams, frogs and birds, herons, short hiking trails, and more. Go to the website for a list of properties, locations and features. Same with the Audubon Society.
Enjoy!
