Yes, there was the potential of danger, but children do transition from needing full-time adult supervision (minus bathroom breaks and sanity breaks) to being responsible for their own safety. Our laws are wrong if they represent the expectation that a 9-year-old needs the same supervision as a 9-month-old or as a 15-year-old. Please, let's not make it harder on our parents and our kids. Give them more leeway than was shown in this incident.
This is most likely the park. Looks nice.