Sometimes it's not even a physical trigger that manifests a dog attack. In another forum there was mention of body language when dealing with varanids, in order to keep them calm.
Children are in a bad position when it comes to body language and dogs.
They are at just the right height to maintain eye contact, which some dogs will take as a sign of aggression.
They have no concept of "personal space". When feeding or resting a dog may choose to be solitary. The child can plunk themselves down within arm's length, and ignore the dog, but still trigger a growl or a snap.
Some children have extreme reactions when startled. If something they do agitates the animal, they may become startled by the animals reaction and exacerbate things by flailing their arms and shrieking.
And, of course, their flesh is less protected. A bite from a dog that wouldn't do much more than drive off another dog, can leave a kid with a some pretty nasty wounds. There's no layer of fur, and we don't have the equivalent of things like the scruff of the neck for a dog to grab.
So then we end up with people blaming the dogs, and others blaming the kids, and it's really not the fault of either.
Good to hear you're one of the attentive owners