Welcome to SR.
If your aim is to have lasting sobriety then for now it has to be your number one priority. That may mean skipping the celebrations for a period of time until you're solid in your sobriety.
Like Weasel says, nobody is making you drink. The only person picking that drink up and drinking it is you. You don't have to do that any more if you don't want to. There's no secret equation for being sober... it's simple - you just have to stop drinking. I'm not saying that's easy, especially at the beginning, and you will probably have to change how you spend your time. But missing a few celebrations is hardly a sacrifice when it comes to your health and your mental well being.
If you want this, you can have it. Believe in yourself. Find that willpower and determination and put sobriety first... put yourself first.
Wishing you all the best.