Parents with small children are usually very busy; they often do not have the free time or desire to spend hours training or walking a high maintenance dog. Initially, puppies require almost as much time as a child does, so ask yourself if you are ready to bring a new puppy into a home that is already too busy. Dogs can help teach a child responsibility, patience, empathy, and compassion, but remember, no young child is capable of properly training or completely caring for a dog, so the parent must always ultimately take full responsibility for the pet.
Make up a set of house rules for the children concerning the new dog and post it on the refrigerator. Decide where the dog will sleep. I personally recommend that a dog sleeps on his own bed (crate) and NOT in the bed with children. I also reccommend that the puppy is not allowed on any furniture.
It is important to remember that in the dog's mind the family is a pack unit and everyone in that family has a certain 'position' in the pack. In most families, one or both of the parents are considered the pack leaders and the dog is subordinate to them. Now depending on the dog, this may be very obvious or it may not really matter much. But when small children are involved, dogs almost always consider the children equal or lower in the pack hierarchy than they are and this is where the problem arises. Because the dog considers the child a subordinate, it may refuse to obey the child's commands or 'accidentally' bump into the child and knock him/her down. It may escalate to growling at the child when the child is near food or toys, or even baring his teeth and biting when the child approaches or tries to play with the dog. It is essential that the parent understands this hierarchal relationship and takes precautions to prevent problems from arising. Such behaviors are an indication that professional help, such as an animal behaviorist would be needed.
Info taken from Pet Education