Just to echo what the others said: do what you can but enjoy the day and your MARRIAGE (not just the wedding). I flew at your weight (and heavier) and had the same experiences Jilly had -- I definitely "fit", but sometimes needed a extender, and did prefer having the armrest up next to me. I also couldn't really use the tray table. Hubby is also big and we took to getting seats that we not next to each other as that was quite uncomfortable at the time... less so now, I think...
I was also a morbidly obese bride, but that didn't stop me from having a great wedding day.
ENJOY!!!!!

Please don't crash diet or try to super-low carb before your wedding or honeymoon. You may be a size or two smaller for your pictures, but the first bite of cake or the first drink will cause you to swell painfully if you've been carb-depleted. It won't be worth the swollen fingers, ankles, and bloated feeling. 

I was close to the same size as you on my wedding and I looked beautiful, if I do say so myself.
Like labelle16352 said, the photographer will do his magic and he will make you look even more beautiful than you already are! 