There are as many ways to narrate as there are children, I think! Take a look at the ideas on this site. For the most part, it is just the retelling in one form or another (and if it’s a drawing or such, you will just get one snapshot of the whole, but that will be what struck their little mind the most). As they get a little experience with retelling, you could ask for things like, what happened first, next, etc., get them to ask you a question or two about the reading, ask what the main idea is, the conclusion, how would Jesus think about this…the list goes on. Also, just the retelling is what will give them the composition skills they need later on.