I know Martian used to offer a checking clinic out of either Phillips Andover or Merrimack College. Not sure they still do, but worth a look.

Check out "4S" hockey
My son has done other clinics with them and do a great job at reasonable price. They run clinics out of Haverhill and Dedham.

So now people are making money on checking clinics? Seriously? Have your team get padded up without skates and wrestle/bump/play tag or have your kid do it at home and toss him around for a couple hours..dont make it a bigger issue than it has to be.
Checking clinics, we gonna talk about Checking clinics, Checking clinics!