I am an author of a children's book that a large organization would like to use to stage an event around

They would recreate the story and add music and read the story during the event - sillier to a play. They would charge a fee to this event. The would then give away the product that come with the book to each child and sell the book at their event. My question is; do they need to pay me a licensing fee for this? The event would be a money making event for this company and they would run this event for 6 weeks. How do I determine how much to charge them for a licensing fee if it is applicable?