Mazel tov! I'm honored to be invited to your wedding! Are you registered anywhere?
It's been a while since we've talked, so I wanted to fill you in on some things before letting you know if I can come to the wedding or not: I'm also engaged, and am getting married this May. We have been living together for about a year. My parents have reacted very badly to the fact that my fiance isn't Jewish, so we aren't on the best of terms right now, and my mother is not speaking to me.
I would very much like to come to your wedding and share in your special day. I don't want to cause a scene or anything with my parents, so if you like I can leave B (my fiance) at home, and come by myself. However, I would prefer that you don't seat me at the same table as my parents.
Another option would be that both me and B could come to the Chuppah, and leave before dinner.
Let me know what you would like me to do. Either way I will try my best to come to at least part of the wedding.