Canada has indeed brought in tobacco control policies that are the envy of the world. You and one or two other places are beacons of achievement in reducing smoking prevalence. We aspire to that.
In Britain we have a complete smoke-free policy for all enclosed public places and workplaces. We haven't gone down the route of banning electronic cigarette use by law in those circumstances.
The argument, as you've pointed out, has two sides to it. On the one hand, we want to protect our children, but on the other hand, exposing children to clusters of smokers outside the buildings and seeing smokers out in the street normalizes the behaviour of smoking, whereas seeing people using vaporizers arguably normalizes the use of vaporizers. Now, that's not say that I want children to grow up aspiring to become a vaporizer user, but I would much rather they aspire to that than aspire to being a smoker.
I think it's quite a difficult balance. The way that I've argued it in the U.K. is that for the most part where smoking is prohibited, so should electronic cigarette use, but it should be a matter of courtesy, not law.
But there are certain circumstances where indoor use would make sense. In that, I would include some hospital areas—for example, mental health settings, where in Britain the smoking prevalence is extremely high—and also the situation I have in my own clinical practice. As a chest physician, I know that my patients are using electronic cigarettes under the covers of the bed because they've been told they can't use them indoors. I think we need to make some system that accommodates that need, rather than have them get out with their drips to go and stand outside and smoke in the rain.