I'm just so sorry to hear this, but glad your daughter had only minor injuries and your GSD is OK.
You can try desensitizing your dog to skateboarders, we have a lot in my area too.
And if your dog won't do a solid recall (like mine) our alternative was a solid "down".
We don't have many off leash areas for training in recall. So down was better for us. We did a special training class with the "down" command. Each dog owner paired up with a trainer and we worked as a team.