How every child doesn't get sick from eating mostly sweets could be due to evolution. Adding to it is that children have been in charge since the stone age.
Word of God says that in the Growing Around universe, sweets don't have any adverse health affects and are basically just regular food. While a sufficient explanation, it doesn't explain why vegetables exist as a food option at all, considering that in Real Life the appeal of sweets is that they taste good in spite of being unhealthy while vegetables are stereotypically the inverse, but here... sweets are just another food group and vegetables serve no specialized purpose (especially since many Real Life adults only eat them because of their nutritional value, and not because of the taste).
Examples of various animals children keep as pets include lions and Komodo dragons, both of which are carnivores that likely won't hesitate to eat a human of any age or size. However, lions are likely tamed, and it is possible that all pet Komodos are raised from eggs. And Dora Tanner's lion Leo is too cowardly to act like every other lion.
Shane's plan in "Pixelotchi" has him produce hundreds of the titular device, which made children too distracted to do anything else (i.e. discipline adults). At worst, the events of the story have a terrifying implication that several children (or at least Sally) would likely starve to death. Even if that wasn't intended, it can still border on Moral Event Horizon in Shane's case. Fortunately, Talula doesn't care about the Pixelotchi to the point of banning them, which puts a hole in his plan.
If children are in charge and adults are the ones who take their place as immature members of society, it leaves one with the disturbing thought that it doesn’t matter how efficient a child is in their work, they’re doomed to become a hapless vulnerable (wo)manchild quite literally at 18 years of age at the absolute LEAST.
