Gatters isn't my usual airport so my experience is relatively limited, but what I have seen is that they tend to be a lot more flexible when additional guests are children vs when it's adults.

Of course, those quietly appoaching the desk and quietly asking "I don't suppose there's any chance - no problem at all if not but thought I'd check" fare a lot better than those parading forwards crotch first in their red trousers proclaiming "BEHOLD MY SHINY SILVER CARD, PEASANTS".