Holidays are tough... it's hard to know when indulging is truly too much. I personally am taking the weekend off as my birthday is Saturday anyways, but as far as a way to limit yourself bring along a water bottle and keep sipping on it. That way you'll have less room in your stomach for food and alcohol. I find seltzer works better, but some people don't like that bloaty feeling from the carbonation.
Just remember to have fun
the rest of our lives will have these holidays and indulgent weekends, so don't make yourself feel bad over it as long as you're doing well on your plan the rest of the year.