You could see if they will let you reduce your availability to 1 or 2 days a week since it's the slow time of year, and then bump up your hours come spring/summer.
Just tell them that you can't survive on the lower hours usually given to TMs this time if year, so you lined up another seasonal job. See if that will fly. Staying will keep your discount and your hire date which will make a slight difference when you get your review and raise.