Alison - there are still plenty of celebratory meals you can have that wont cause such a spike, dont lose heart.
I know how you feel, I never forget a wedding I attended first time after I started low carb, I thought I had made some reasonable choices from the buffet, etc, only tiny bit of dessert and cake, I cried buckets later when I tested 21.4, not in my wildest dreams did I think that ti would be this bad.
At the time I was still taking Gliclazide, Metformin had been stopped because of kidney disease - makes me shudder to think back.
All the best, and happy birthday to hubby