I have long drive and parent park right next to front door, maybe 6 feet away from door. I think if parent was leaving child in car to go into store or even on main road would be different. I not sure if it illegal here or not when parent in such close proximity. No different really than strapping child in car seat while they brush snow off car in Winter.
Add - Found this. It say only Quebec is age for leaving child in car which must be 7. Nothing for Ontario. Page 3 has table.
http://cwrp.ca/sites/default/files/p...ns/en/144e.pdf