If a child is hit by a car that would be really tragic and horrible for everyone. That is why there is a by law about not allowing unsupervised children in hazardous areas, eg. Where vehicles are moving around. It’s not just insurance questions. What if a child is seriously injured or killed? Both the family and the person who hit them would be damaged. I (lay person) read the by law as obviously hazardous areas are not play areas and adults should walk their children through eg. When coming home, parking and moving to your home. Strata tends to be medium to high density areas, ie. With traffic. There is also the issue of damaging people’s cars if throwing balls or riding bikes.
In my block people complain about kids playing in the car park or being unsupervised (usually because of the noise which can be irritating if they’re running up and down stairs for example). I usually like the sound of children and feel for the kids. (I grew up in a rural area with plenty of area to roam and frolic). Our strata has a park nearby but parents don’t always take their kids out or supervise them.
We installed a safety mirror so cars can see around the corner and it’s a little bit safer. We could try a speed limit sign or slowing devices as someone else suggested. Signs warning to look out for children could help too. We might even get our driveway gate fixed. There’s not really room for a play area on the property.
So, to answer the question, as others have said, no it’s not discriminatory. It’s about looking after the interests of everyone in the building.