How do I tell my parents I want SRS?

For the past four months I've been going to therapy to get approved for my MTF SRS and my theripist says I need to live a year as a woman and suggests I tell my family. I have no problem living as a woman but the prospect of actually telling my parents (espically my dad) fills me with fear. When I think about it I want to just run away and never return. Any advice here would be helpful.