I'm not attending my cousins wedding

I had planned to attend a convention with 3 really good friends last year, it was canceled so we planned on going to it this year. it just happened to fall on the weekend of my cousin's wedding. The convention is in California, and the wedding is not. So it is a trip I planned on taking for two years with my friends. I just told my cousin I was not going, my wife is still attending, my Aunt is pissed. Was I wrong to not give up the trip?