I would be suggesting that the following bylaw be proposed for adoption at the general meeting:
“(2) An owner or occupier of a lot must not permit any child for whom the owner or occupier is responsible, unless accompanied by an adult exercising effective control, to be or remain on common property that is a laundry, car parking area or other area of possible danger or hazard to children.”
Then, if the problem persists, you have a breach of a bylaw that is clear and explicit and recently adopted in the light of the current problem. That should make it far easier, if necessary, to demonstrate to both insurers and the Tribunal that the OC has considered the matter and is taking action.
BTW. If there are areas of common property in which children can generally play harmlessly, then I would adjust the wording to just exclude the carpark. I would not want children to be prevented from having harmless unstructured unsupervised play.