I must confess that I am a candlepin bowling afficionado and have only done “big ball” bowling twice in my life.
But if big ball is your thing, you can sign your kids (age 15 and under) up for free bowling at AMF. Once you register, you’ll get a weekly voucher for two free games per child per day through September 3, based on lane availability. Shoe rental is not included.
(I will remain faithful to the famously air-conditioned Colonial Bowl.)
Nicole, Worcester 
There’s a similar program at http://www.kidsbowlfree.com/state.php?state=MA which includes some candlepin lanes. I know Bayberry Bowling in Spencer is candlepin. I haven’t been to any of the others.
Thanks! I know French King in Erving is candlepin as well.
here’s the full list of Candlepin places. http://www.masscandlepin.com/id30.html