I don't buy the "eating healthy is more than they can afford" bit -- "afford" is simply a matter of you saying "you can afford it," and then prioritizing it. That means you prioritize healthy food for your family, or you don't. If parents eat out at restaurants more than once a month, go to the bar once in a while, have cable/TV packages/buy Blu-Ray movies, then they can "afford" healthy food-- they just choose not to prioritize buying it.
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To use your pop/soda argument, the SAME amount of money could be spent on milk or 3-dozen eggs at Costco. Your comment "Eating at McDonalds is cheaper than cooking a healthy meal at home" is bogus.
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You JUST got done declaring about the health epidemic and costs to our society-- the question you should be asking is, "how can you NOT afford to eat healthy?"
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Parents should be teaching their children healthy eating and exercise, and should model that behavior to them-- that does NOT cost a lot.