General strategies for handling geese
First, never taunt or harass your geese, and do not allow children to do so, either. Waterfowl thrive in calm, quiet environments, but will learn to be aggressive if aggression is directed toward them. Work quietly and slowly among them, never making fast or threatening advances. It is likely wise to avoid overly-taming them as well, as some may lose their fear of humans altogether and begin to feel very comfortable challenging you. If one does move toward you aggressively, do not fight them or swat at them, since this can just make their fight instinct stronger. Also, do not run away, because this gives them more confidence, and they will likely chase you. Instead, stand still, and do not turn your back. Most of the time, they are "more bark than bite." When you provide the bird no stimulus to fight, they will usually calm down and retreat.
Sebastopol geese are among the least aggressive breeds.