Hi there. I don't know if my experience and thoughts during a semi-similar situation will help you, but here it goes:
After 7.5 months of sobriety, I started drinking again in late June during a personal tragedy. Shortly thereafter, in July, I had several pre-planned vacations. One was a family beach trip on the East Coast and one was a friend's wedding with my sister on the West Coast.
At the time, I was thinking, well good thing I'm drinking again because I would feel like such a bump on the log if I were to do these things sober. Almost everyone in my family drinks (except my mom) and during the beach vacation my dad, siblings and our significant others would go out drinking or stay in drinking pretty much every night, and we would also drink a lot on the beach during the day. We did things like karaoke, playing board games, going to a bar for a UFC fight, heck even playing mini golf with our younger siblings, that all seemed to be more "fun" with drinking, and I thought, oh boy I would hate to be sitting here sober with all these drunk people, and they would think I was so boring!!!
Same thing with the wedding... there was free wine and beer all night/day long, and everyone else was drinking. A wedding is one of those places were it's "acceptable" to drink a lot, and everyone seems to be doing it, even those people who otherwise don't drink often/much. I was dancing and laughing and thinking, oh my god I wouldn't have nearly as much fun if I were not drinking! I don't know how I'd make it through!
But you know what. Inside I wasn't very happy and was in fact disappointed with myself for giving up on my goal of sobriety. Looking back, and even at the time, I am/was ashamed of my actions while drunk. I feel bad that my younger siblings see us drinking all the time, and for awhile I had been a good influence on them but now I was one of the people whose reaction times and mannerisms were off while I was around them or even taking care of them, because I was drinking. I couldn't just relax or enjoy their company or time with my mom who doesn't drink etc. And at the wedding, I was silly and made a fool out of myself and even if everyone else was too drunk to notice, *I* noticed/know, and to me my own opinion of myself is what matters.
So basically I regret drinking and am now trying to avoid events that might tempt me. If I have to go then I try to remember my goals and priorities. I'm also looking at why I think I can't have fun at these events unless I drink, and why I care so much whether other people think I'm lame etc. I need to be confident in myself sober, which is an "underlying issue" that leads me to drink. Best wishes to you, you can do this, and congrats to your friend.