They had to know they had a possibility of playing on weekends right? If they can't make arrangements to play later, forfeit. If there beliefs are more important than a game, this shouldn't be a question.
I would NEVER skip playing in a championship game because of religious beliefs. Championship games come very infrequently, if ever; the sabbath comes every week of your life in pretty much every religion.
I believe my God is a god who forgives us of our sins. I'm pretty sure he'd understand, especially if I attempted to absolve myself the following week...