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Can I say,

They are having a reunion dinner at / before the eve of Chinese New Year.

They are eating a reunion lunch on the eve of Chinese New Year.
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They are having a reunion dinner on the eve of Chinese New Year.

They are eating a reunion lunch on the eve of Chinese New Year.
Comments  
Teachers: We supply a list of EFL job vacancies
Thanks. How about this?

They are having reunion on the eve of New Year.
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They are having a reunion on New Year's Eve.