Over 30 years ago I worked with a woman that got hit by a bicyclist at Venice Beach in LA- same beach as in this video, I think-and she was laid up for 6 months. Broken jaw, collar-bone, arm, really hurt.
If you are flying around in a public, heavily populated place, you need to watch where you are going. Especially for little kids; they sometimes don't look out for themselves. For a parent, you see you child get bowled over, what do you do? In that first flash of protective aggression, I'd have broke the board over his head.