My dad is a pedophile...what do I do?

I found out my dad was a pedophile a while ago (4 years) but I have never had the guts to confront the situation.
Now I'm 17 and can't do it any longer.
I spoke to my nan who said she'd talk to him and tell him about what he said.
But now I don't know what to do?
What if I see him in public?
What if he seeks me out? 
Plus should I tell his fiancé?
Because what if they have children..?
He is also a selector in a major football league and is in a high position of power.
What do I do?!