I could make the point that pollution by vehicles is also about basic courtesy and reasonable behaviour in shared public spaces, but it has become so normalised

I could make the point that pollution by vehicles is also about basic courtesy and reasonable behaviour in shared public spaces, but it has become so normalised that I don't think you'll be convinced. However, I do agree that people should be more wary around children and not subject them to second-hand smoke. The problem is that cannabis has such a strong smell that the smell is noticeable even when the amount of smoke exposure is likely not measurable.