We have had several different dogs. A Lab is our dog of choice. Do not go for a full bread as they will likely be in bread and have medical problems.
My wife has done day care and our different dogs have been around many children and have had ears and tails pulled and no one has been bit.
The most amazing thing is their ability to know who is ok and who is not. With day care parents and kids coming and going our labs easily learned who was supposed to be at our farm and who was not. They all had a controlled bark reflex. In which they only barked when there was a reason, and were not yappy dogs.
We had one lab mixed with dane that was around here for one year that I shot after he tried to attack my daughter in our living room. I would stay away from lab and dane mix.
DO NOT TAKE A MIDDLE AGED DOG THAT WAS RAISED BY ANOTHER FAMILY AND TRY TO ACCLIMATE IT TO YOUR FAMILY. IT WILL NOT WORK.