How to ask my dad not to speak at my school?

I'm a senior and next week they're doing an assembly on addiction and my dad told me he was gonna be a guest speaker. Nobody knows anything about my dad. They don't know anything about my real parents. Me and my dad have a 15 year age gap and me and my biological mother have a 23 year age gap so you can do the math on that. I was born in prison and my dad's sister adopted me and she's the only mom I've known. I've always known who my dad was and stuff but he was on drugs for years. He was also a male prostitute and I remember being 9 and my mom(adoptive mom) yelling at my dad because she was sure he bought my birthday present with drug and or prostitution money. My mom never wanted me to grow up hating my dad and told me he loves me so much and it's why he let her adopt me because he didn't have the resources to help a single dad at 15 and was struggling with addiction. He's been sober for 7 years now and we have a decent relationship. We see and talk to each other regularly. My dad isn't a bad guy but I haven't told anyone about him and I don't want him speaking at my school. I don't know everything he's gonna say. I don't know if people will piece together that he's my father but I don't want to be known as the girl with the drug addict/child prostitute/male prostitute father. I know that I graduate in May and none of this will matter but my senior year is important to me and I don't want it tainted.