It could be worse. I had to go to a UGA wedding last weekend and had to miss the UNC vs. GT game. Not to mention, my wife had to wear a red bridesmaid dress with silver shoes because their wedding was UGA themed and the Groom's Cake was UGA with a bulldog next to it and a football on top. Don't even get me started...
Here's the deal. You put the tickets on craigslist (had to do this two years ago) and for everyone that responds, make sure they are GT fans. The good thing about craigslist is that you have to sell it to the person face-to-face. So you can figure out if they are GT fans right there. I coincidentally had to do this with some VT tickets two years ago. When I met the potential buyers, I asked the major, who some of their professors were to make sure they weren't lying, etc. After confirming they were GT fans/alumni, I sold 'em.
Then you can use $3.00 of the money you made selling the tickets to buy a wedding card that explains your disgust with the wedding. You don't give them a wedding present because of your inconvenience, you watch the GT vs. VT on your cell phone during the ceremony and the reception, and you drink as much booze as possible during the reception on their dollar.
As I said, it could be much worse. You could have to go to a UGA themed wedding where your wife has to wear UGA themed clothes in the bridal party and you have to listen to the f-ing UGA fight song at the reception and rehearsal dinner. Not fun.