When someone goes out of their way to do something nice for you because you asked, when they spend dozens of hours on something which benefits you completely and not them at all, and when that person has successfully done this chore dozens of times in the past, don't insult them by implying they are useless and incompetent 12 hours before the event.
Forget wedding etiquette, how about just trying to be a decent person? How about just giving a damn about the feelings of someone else.