You can control and censor a child's reading, but you can't control her interpretations; no one can guess how a message that to adults seems banal or ridiculous or outmoded will alter itself and evolve inside the darkness of a child's heart.
Concentrate your narrative energy on the point of change. This is especially important for historical fiction. When your character is new to a place, or things alter around them, that's the point to step back and fill in the details of their world.