So they're not supposed to share in their friend's joy because of their dad's politics?! they're adult women who get to make their own decisions, their own friends, and attend the wedding of their chosing. This won't make W look bad, it shows that he raised polite kids that aren't going to let beltway BS get in between them and their friends.
Attending a gay wedding is a bit much. Face it, it's a mockery of God. You can't attend a same-sex wedding and honestly honor God. Let them live their lives gay if they want and tolerate it, but marriage is not acceptable.