Should I have a lawyer for child custody mediation?

My kids’ mother and I are fighting over custody. She filed a custody complaint in Charlotte family court and I just received a notice that I’m required to go to mediation with her. I have strong evidence that I want to be able to use against her in court and I don’t want her knowing what I have before we go to a custody trial. Do I have to share everything I have on her in mediation and should I have a lawyer present with me?