Wow ladies, thanks so much for all the great comments... Here's an update.
I called my dad last night, and told him I needed to talk to him. I think he could tell I was upset about something. I asked him flat out if he had plans to get married in Maui the same weekend as my wedding. He hesitated, but then claimed that he had said that, but he was only joking. I don't know if he was joking or not (i think he was just backing out of it because he could tell how upset I was).
One of you mentioned that "family dynamics" has a lot to do with the situation. I totally agree. My dad has a very strong history of wanting to be the center of attention, being very self centered, and always needing a situation to be about him. That being said, that is why I was so upset at the idea of him getting married on the same weekend as me.
I realize that we only get "one day". I don't expect more than that. But, my father's history of thunder stealing really made this situation a very sensitive one. I would not be upset if a friend/sister/mother, or anyone else in my family chose to marry that same weekend. But my father's track record of not taking marriage seriously and needing to be the center of attention makes this a different situation.
Thanks so much ladies for your great advice. It really helps!!