Basic rule: dogs are pack animals and puppies are dogs
If you and your family do not become the pack leader then your puppy will eventually assume that roll. This is the basis of most dog behavior problems. Your puppy started learning pack rules the moment it was born and will continue its education until the day it dies. I know your are busy, tired and have more important things to do but, as with children and animals, bad habits left uncorrected lead to worse problems with time.
Your new puppy and the children already living in your home are your responsibility. They must both be taught to coexist with each other. This is not, let me repeat, NOT a one way street for the dog. Children with dogs should be supervised. There should be do's and don'ts for your dog as well as your children. Depending on temperament, when subjected to cruelty or pain dogs will either flee or defend themselves .
To ensure peace, you must become the pack leader of your family and each family member must in turn become the pack leader of your dog. Pack leaders are not viscous or cruel. Nor are they brutal. They are however stern and consistent. This physiology works equally well with children as with dogs. Children and dogs alike understand authority and consistency. Dogs however understand and react differently to situations than children. You might want to pick up on some basic dog physiology tips. Oh, I am sorry. I forget to tell you that bringing a dog into your home was not going to be easy?
Training, is teaching your dog the manners and behaviors you expect and will accept. Some people accept their dogs sleeping on furniture while others do not. What is acceptable in one household is not in another. It's just a pack leader preference. You need to teach your dog how to live with you through love, respect and consistency. Pity, feeling sorry for and giving in to your dogs actions will become your downfall and cause you and your dog mounting problems later on.
Training should not be regimented, boring or stern. Vizslas do not require heavy handed training. If you feel your Vizsla requires harsh training methods you didn't do your homework before you purchased it. Using heavy handed and harsh training methods could destroy that wonderful temperament you have heard so much about. Training should be a fun way to teach and communicate. Your training should be ongoing and constant as your dog is always in the adjusting mode (unless it is asleep of course). Exercise, training and supervision are your keys to having a wonderful Vizsla. Remember!! Your Vizsla is a sporting breed, don't forget the exercise.
Most behavior problems can be solved and should not be allow to continue. Seek competent help with any problems you experience and don't be offended if you find the problem was brought on by yourself. It happens to the best of us. Sometimes over training can cause problems also.