I don't want to mediate my parents' divorce
Why don't you want to help your parents mediate their divorce?
I feel mediating them is wrong because it's their own business
It is good to stay neutral when dealing with the break up of parents. You should not take sides in a divorce.
Yeah, it's annoying that they want me to mediate their divorce. They should be able to do it themselves.
It's wrong of them to want to put you in the middle of their divorce. It's OK for parents to choose to get divorced, but they need to be conscientious of how the divorce will affect their children. I hope that they back down and leave you out of it, otherwise you may grow to resent them.