Should I sing at the non-Catholic mass?

I’m a freshman in high school and just joined the choir there, and apparently we’re taking a trip to Hawaii for a competition on Holy Saturday for eight days. I told my choir director that if I could not go to Mass on Easter Sunday then respectfully I would decline the offer of going to Hawaii, but he said he would take care of it.
Later I heard him talking to someone else about possibly being able to sing at one of the masses however it would be non-Catholic probably. I couldn’t help but feel uncomfortable about this. Should I? My sister told me that if I happen to find myself going to a mass that was not Catholic, i should just sit down the whole time and not really move. But to volunteer my services in helping a cause I don’t believe in, like a non-catholic mass as a choir member? I think it’s overstepping but I’m very ignorant, I need advice on what to do. I’d be making a scene by refusing to sing on that occasion, but if that’s the right thing to do then I’ll do it. Please let me know…

This link should be helpful for understanding what role Catholics may have in non-Catholic services. If you have any further questions or concerns that are not answered by this link, please contact Catholic Answers directly.
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