I can tell you that as a writer and as a reader, I regard character as king. Or queen. No matter how riveting the action or interesting the plot twists, if I don't feel like I'm meeting someone who feels real, I'm not going to be compelled to read further.
The worst mistake you can make with children is to talk to them in a condescending, patronising way and think that you can teach them something. You have to understand that it is you who will be learning from them. You have to get into their world and see things from their perspective.