I think the evidence that best supports the conclusion that the narrator is telling this story with a particular child in mind is the repetitive use of the second person, addressing directly to the reader.
In addition to this, the excerpt “But once a year all Pau Ammas must shake off their hard armour and be soft—to remind them of what the Eldest Magician could do” sounds like a recommendation or a duty of all Paul Ammas, that the narrator is telling the addressed person that he7she should fulfill as a Pau Ammas.
