Sorry to take so long to reply the dog wanted a walk.
Concentrating on the dog and its breed and its training is totally irrelevant to the risk of a child becoming harmed by it. It may actually be the child's interactions with the dog that sparks the fury. Like the spud gun you think is over egged at moderate risk though it could blind a child if the child shot himself in the eye with it. So with a well trained never hurt a fly dog being battered with a toy train set, bit in the genitals or having a bottle stuffed up its jacks , it may well react differently.
In law there is something called a reasonable parent test. The only question in this case is would a reasonable parent allow their three year old child to be left alone with a large strong toothed carnivorous animal. (Anyone quoting Mr and Mrs Darling is in the land of the fairies!)