I would think about it short term:
How would the classes be? Mandarin would be harder than Latin…is that taken into account? Would you be starting in Mandarin 1?
And also long term:
When you are an adult, will you be visiting your relatives? Will you be wishing you had taken it?
How likely it is that you will actually read the classics in Latin?
Seems like learning Mandarin would be more useful for family and possible business purposes.
Latin would only be useful if you are majoring in classics or perhaps medicine.