you can trust dogs as much as you can trust a baby or child. Which is to say not at all. Kids may be angels 90% of the time, but they can be unpredictable - they can pull hair, bite, poke eyes at the drop of a hat (sometimes without meaning too). The same goes for animals. They may be most placid, children loving, proctectors of your children, but they may do the unpredictable, it may not even be their fault. The dog might have been hurt by the child, they may be getting old and dementia is setting in, they may have a toothache you are unaware of, they may just be playing and simplly be too rough.
I have a 4yr old labrador who is the best dog you will ever find for children. My 2.5yr old and my 4.5yr old are allowed to play outside unsupervised with her - She does not bite even when her hair is being pulled, and she is a very obedient dog. Having said that we have had tears a few times simply because she is so much bigger then the kids and knocks them over when she is too excited. The lab is not allowed anywhere near the baby unsupervised.
We now have a beagle who also seems to be great with kids, however only the 4.5yr old is allowed outside with her unsupervised until she is a bit older - but even then I have raced outside a feww times to tears, because the dog is too excited and jumping on my DD. The dog is just over 1yr old and still in the puppy stage - as such she sometimes 'nips' as part of play. The 2.5 yr old is allowed supervised play with her. The beagle is only allowed near the baby if the baby is being held by an adult. (the dog is much to excitable).
So it really does depend on the dog and the children, but even then an adult should never be out of ear shot.
