This by-law strikes me as a bit too vague. A driveway in one strata site could absolutely be somewhere you would not want children to play, supervised or not. A different driveway somewhere else could be an ideal shared common property space that presents very little danger (though anywhere shared with vehicles would have some). It could be the best place for kids to ride scooters or play a ball game. Why not install some traffic calming measures if needed at the site? An engineered safety solution is always better than a regulatory one.
The by-law is also vague with potential over-reach. Is a 12 year old walking home from school and up the driveway going to need to arrange supervision for the last bit of their journey lest they be in breach of the by-law?
It seems to me that each OC should work out whether they need such a rule for specific areas presenting real risk and if there is a risk, whether that risk could be minimised some other way than through a by-law.