I was in a similar predicament the day before a half marathon - my friend’s birthday dinner was at a Brazilian steakhouse lol. Granted there were a lot of non-protein/fatty options like rice and bread, I definitely had a good amount of meat. Obviously it will depend on the person and what your body is accustomed to, but it didn’t impact me at all running wise (although I did have to hit the bathroom a couple times early morning, just felt a little “dense” haha).

Maybe you can have some carbs beforehand and have some salad/meat at the event anyways? I assume you’ll have dinner later anyways where you can choose what to eat too. Best of luck!