When we ask parents if their children are obese, they don't usually see it that way. It's a perception problem, and you're entirely right in saying that you have to start by showing people what obesity is and what tendency their children are following.
I think a significant information campaign must be conducted on this. Surveys have been conducted on this subject and have shown that parents don't see their children accurately.
In addition, there is a tax on junk food in 16 American states. We wouldn't be reinventing the wheel, since this is done and has already been done outside Canada, in other countries.