I'm 13 and I currently study at a Kenpo Karate school, and I understand where you're coming fomr, my mom was VERY hesitant to let me compete becuase I have ADHD and my temper is on a VERY short fuse. Over the years, I have learned that ANY child, no matter the age or style or skill or rank, is able to compete. IT IS ALL ABOUT CONTROL. If there is no control, the child should not compete. My instructor has talked to me many times about this, before every tournament actually. He always tells me, "Just shake it off. If you lose, appreciate the fact that someone was better than you, or that someone was able to strike more skillfully. Shake it off and smile, knowing there is room to grow."
Also, I personally believe that it is essential to HAVE FUN. If there is no fun, you're wasting your time and everyone else's time.
hope that helped