17. Become a proper Ninja
Take your ninja skills to the next level (or your kid’s skills, in this case) and learn the martial arts! Again, the answers are all found online: there are plenty of virtual classes for the different martial arts, Karate, Taekwondo and others, less popular forms.
Make time every day (15 to 30 minutes are more than enough) to watch online tutorials on the different martial arts or the one you wish to learn, and then spend a little more time practicing what you’ve learned that day.