I always rode my bike on the road as a kid, but in saying that we lived in a cul de sac of about 5 houses, so traffic was rare. For everything else we played in the yard. We were fortunate to have a decent size backyard though. Not like yards these days.
Now, we live in a gated complex and the kids are always playing on the 'roads' and I hate it. Even though our speed limit is 5km/hr while in the complex, people still fly around the corners doing at least 20-30km/hr. DH has had kids run in front of him without looking making him brake. Plus one of the kids is an amputee with a prosthetic leg, so he's a bit slower than the average kid to get out of the way. The worst part is that majority of the time the parents aren't supervising them because they obviously figure it's "safe" because it's a gated estate. Even though it's part of the body corp rules that there is to be no playing on the roadways, people don't care. It will take a kid getting hit for people to change their behaviours.
To the lady who said it was her kid's right to play on the road, I sincerely hope she never goes through the trauma of losing a child/ having a child seriously injured who has been struck by a car while playing on the road. Roads are definitely a cars domain. If it was a quiet street I wouldn't have an issue if they were playing safely. On a road as described in the OP, play at your own peril I reckon.