That's how government gets control of people, give them something and then tie strings to it. It works everytime.
Secondly, who decides what is "trash" food? And thirdly, they aren't "our" children or "our" people. People own themselves, they are not owned by society.
The government has no legitimate business whatsoever in these things.
Who decides what is 'trash' air? Is it really necessary to restrict refuse-burning plants from being constructed next to elementary schools?
I appreciate your purism; I also believe that the main reason we've become an overweight, unhealthy people is gov-sponsored/sanctioned bad nutrition.
Here: let's define 'trash' food as 'processed' food for this point of argument.