What if the day came that a very powerful extraterrestrial came to earth and decided that children of Earth are going to make all the decisions from now on. what would happen?
It will end very badly, as ?all? most implementations of Jean Jacque Rousseau's philosophy have. Ask the victims of the Khmer Rouge, who empowered children to make life and death decisions, because of their purity and lack of contamination. Read about the tragedies of Cambodia, whose government believed that children are naturally born pure, but corrupted later. It is naive in the extreme to think uneducated, untested and inexperienced people will automatically solve our problems and create a utopia.
Everybody is somebody's child...
So technically the children of Earth already run the planet..
Now, if you meant. YOUNG children.. then..
Nap time would replace work starting around 2ish, the food pyramid would be desserts and every day would be halloween or christmas.
Also, huge playgrounds would replace schools and other "boring" places.