How do I tell my dad he won't be walking me down the aisle?

My mom and dad divorced before I was born. My dad was very active in my life until he lost his job when I was 12. Since then my dad has not really had a lot to do with me because he stopped paying child support and there was a lot tension between him and my mom. I just have no idea why he became so distant after that. I just gave up on trying to be in his life because he never tried to be in mine. I still love him because he is my father but I've never really felt like he actually took care of me and cared for me like a father should. And that's fine, I've accepted it. I have chosen my brother to walk me down the aisle because he has been more of a dad than my real dad has ever been. I recently found out my dad plans to attend my wedding. I have a really soft heart and don't want to hurt his feelings but I really want the person who has always played that father like role to walk me down the aisle. That's important to me. I just don't know how to break it to my dad. Advice?