Fiction is often escapist and written and read for entertainment. This is fine. However, I believe children’s books should be truthful about the consequences of action.
Children, though, don’t have that much experience. If a child reads a book where a bully is “cured” by Little Tina explaining how her sister felt when the bully stole her lunch and expects that to happen in real life, then that child is set up for ridicule or worse. If a child reads books in which every child who confesses to doing something wrong is praised for being truthful, then what happens when s/he confesses and is punished?
4. A children’s book should show a balance of characters with a wide variety of abilities, attitudes and beliefs. Avoid the obvious. Let there be some nerds who do not wear thick glasses. Let there be grandparents who are not old and retired. Let there be mothers who are sometimes busy, dads who ride bikes to work, teachers who occasionally don’t know something, and doctors who do not have an appointment as soon as you need one. Let the occasional standoffish new kid continue to be standoffish and the one who claims to be good at singing really win that competition.
This may appear to run counter to the advice about genre, but in fact it helps bust those stereotypes and lets a genre book transcend that genre.