In the church I attend, there are a few not-so-little ones (ages 3-6) who, more often than not, are rather loud and full of beans. I've noticed that when the mothers are getting nowhere, other (usually older) women (with the mother's permission) need only catch the eye of the child, and do something as simple as raise a finger to their lips and look at him/her a certain way (not angrily), and the kid cuts it out.
Small babies are a different story, and nobody minds too much when they make their presence felt. It's the toddlers and slightly older ones who respond best to an "auntie" gently letting them know that their antics are "not on".