RE: Safe to fly in school yard?
Some folks are obsessed with the "little ones" and don't think anyone should have any fun at all if they aren't obsessing over the "little ones" themselves.
You're obviously attentive to folks coming onto the field and won't fly when kids are playing sports there so I don't see it as a big deal. And you've like brought far more smiles to kids than you've endangered by the sounds of it.