You can even say, Please don't pour any for me, I'm not drinking. That way, you won't be drinking 'your' champagne, you won't be drinking any champagne at all.
I suggest you walking through the whole evening in your mind, like watching a movie, so you can visualize yourself in that situation, what you will do, what you will choose instead of wine, how you will feel, what you can do if you start to get dizzy. Please consider a plan B. Will you excuse yourself? Leave the party? Go for a little air to settle yourself?
You can do this, I know. A plan is still a good idea.