I have had the priveledge to have been around many different breeds of dog. I have found over the years that the Labrador Retriever is the most friendliest, playful, and protector to have around childen.
My lab lets the kids climb all over him and he has never complained once. They pull on his tail and his ears and he just lays there. We also have a lab puppy that bites him all over and he sits there and lts her do it.