The issue isn't the change in throwing distance. The issue is pitching for two teams at the same time. It wouldn't be my son. At ten he played rec in the spring and travel in the summer. At ten years old I only let kids pitch two innings a week.
No one remembers the preteen studs other than "isn't it a shame he destroyed his arm pitching too much." No player ever got to the mound in high school based on being a preteen stud.