Golden Retriever seems the one that comes to mind automatically, but I think Newfoundland mixes are a very good choice for a home with children. The breed is known to be “patient, playful, and loving with children; he is a born babysitter. Very sociable.” (from http://www.dogbreedinfo.com/newfoundland.htm)
I’ve never seen one bite, snarl, or act out any type of aggression toward a child. In fact, in the original Peter Pan “Nana”, the children’s “nurse” was a Newfoundland.
I used to have a mixed Newfie, and the only time I can remember anyone being afraid of her, was when a plumber was walking into the house (a fairly short man to begin with), and he bent over to take off his shoes in the doorway. My dog saw this as an invitation to play outside, and jumped over him, and ran outside. He was a little shook up, but she didn’t even touch him.
The reasons I recommend a mixed breed Newfie: for one thing, they are easier to find at rescue shelters, human associations, etc, than pure-breeds; mixed breed dogs tend to live longer and be healthier; and pure-bred newfoundlands can be up to 150 lbs, and shed a ton. It’s a little large for the average household. If you get a mixed breed they’re generally a little smaller (ours was 70 lbs) and don’t shed quite as much.