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…

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