Steve - at the age of one year, Waunoka should not be showing ANY aggression toward people on his walks. He is entering (has entered) his adolescence and, like any teen-ager, is going to test the limits of his behavior - and your patience. Growling at children at any time is completely unacceptable, and you have to let him know that.
Before I - and others on the list - go into techniques for altering his behavior, let's review proper guardian behavior. The Great Pyrenees is one of the Livestock Guardian Breeds that has been developed for millennia as territorial guardians. This means that they will protect anything (including themselves) in what they perceive to be their territory. When the dogs wandered long distances with their nomadic flocks, it made sense for them to be hostile toward anything they met. In non-nomadic situations, the dogs need to learn the limits of their territory.
In any pack, it is the Alpha that decides the limit of the pack territory. Not to define - and respect - territory boundries would mean that fights over territory would interfere with more important activities such as eating and reproduction. In your "pack" you are (or should be) the Alpha. Your "territory" is defined as your house and back yard. When you are out walking you are outside your territory. You are always aware that there may be dangers, but you don't provoke confrontations. When you pass other people you either smile (to signal non-aggression) or deliberately avoid eye contact with those that may not be friendly.
Your pup must learn to respect the rules of his Alpha's territory. This means he may not act aggressively toward those he meets outside his territory. (Aggression on his own territory is another topic.) At one year, he's not experienced enough to be allowed to use his own judgment about what is and isn't a threat and he must be shown, firmly, that you are in charge and you are making these decisions for both of you. If you are walking in neighborhoods where you are uncomfortable, this is transmitted to the dog. Find another place to walk until his training is completed - around 18 - 24 months of age.
If you haven't already, get your pup to obedience class. You will get help there in socializing him; even pups with one session of class under their collars can benefit from another series during adolescence. If you haven't already - and you don't have an agreement with his breeder to the contrary - have him neutered. This will remove the hormonal component that contributes to his confusion, and will not interfere with his being protective when the situation warrents.