My sleep pattersn were bad also when I stopped drinking. My mind had to get used to being tired and staying asleep for 8 hours. I also had some terrible nightmares for a while, but that passed thankfully. It's just a matter of time.
Like you, I also had a wedding to go to and I knew there would be drinking involved. Laughter is the best medicine. I called my friend Mitch from rehab and he told me:
"When I get married I'm going to have an 8 hour ceremony with no booze. That way everyone will be miserable."
I laughed so hard I almost wet myself.