E.M.
for my daughter's 3rd birthday, we had it at My Gym, which unfortunately is closing. (But, they have a My gym in Newton, too). She LOVED her party there, it was lots of fun.
We have been on playdates at Playtown Express, and we had her 4th B'day party at pump it up - seems like every kid in her preschool class had their party there - super fun and we did't have to do a thing, staff did everything for us - super easy!
good luck!