D.B.
There's not much in Westboro, which has been a problem for us for years! (My son is almost 20 so we've been lamenting this issue for ages!)
There is a small playground at the new Green Thumb greenhouse center on Route 9 between Lyman St and Route 135 - it's on the westbound side. There is a tiny petting zoo with a couple of goats and a donkey - might be your daughter's speed!
There is an animal area at Harvey's Garden Center on Route 135 East, off the rotary about 1/2 mile going toward Hopkinton from the intersection of Routes 30 and 135. There are quite a few animals in the fenced area, a few bunnies in the area near the parking lot, a large model train area, and many ducks/swans in the pond. You can feed the ducks from the covered bridge - when the weather gets warmer, you can see catfish come up from the bottom to get what the ducks miss! You can purchase food in small bags in the garden center. There are different foods for the ducks vs the other animals - I think the main difference is that the duck food floats, which is important. There are some exotic fowl too - they can be fed thru a pipe that leads from outside the fence into the caged area. Your child is obviously too young to feed them but might enjoy it while you do.
There is a playground in Northboro at the intersection of Routes 20 and 135 with parking on the side street.
Good luck and enjoy the warm weather with your little one!