Selling items at a performance?

We have licensed Shrek Jr with MTI. We will be performing this production on Aug 4,5,6 and 11,12,13. We were contacted by the company HeartlandCostumes.com. They have items that you can purchase to sell at your event as a fund raiser. They offered shrek like green ear head bands to us for a cost. They do NOT say Shrek on them anywhere. We wanted to check with MTI to see if this is alright to do as a fund raiser?