I'm not sure if Charles ever published the soccer training materials, Coach Jance would be able to answer that one a bit better. As for general advice, keep in mind that during the early adolescent / pre-teen years you have a very unique window of being able to influence their maximum ceiling for alactic / explosive potential moreso than any other phase of life. This means medball throws, jumps, and short sprints with full recovery should be a major component. Think high power output / low skill exercises that are simple to teach and easy for them to understand and perform well. In the weight room, teaching proper lifting technique takes precedence to lay a foundation for future hard phases. Keep the program super simple and only progress them in load when they demonstrate perfect technique. No need to do complicated exercise rotations, or get too crazy with periodization schemes. Focus on a handful of basic exercises and get them to do these exercises well and you can't go wrong!