I think having children be the attendants is a wonderful tradition. Keeps them from being bored during the ceremony .
They shouldn't be at the ceremony at all. Or at the reception.
I never like it when you're at a lovely reception and restless kids are running around the dance floor, bumping into people.
Most weddings I have attended recently make it a point to exclude children.
(I heard William's antics so dismayed the Queen that she insisted on a new governess for him, because she thought he was out of control).