What are the "official" rules and "best" guidelines for horse soccer? - online horse games for kids

I ordered a set of Parelli horsemanship and want our football team in the country began drilling riding. They have a need for fun, "a" departure from normal practice. We have tried and most of the children and the horses seem to enjoy. However, since I bought the ball from a location other than the official rules horsesoccer.com site. I searched but could not place any "official" rules in line at will. Please let me know how your group is a game. How often a player? Thank you!