Don't know exactly how young you intend, but this should work through the second grade at least, if memory serves.
Young children have an incredible ability to focus huge amounts of attention on very small things, and they like rereading. If I were writing (and illustrating) a children's book, I would do two things. First, repeat the same action over and over again, with different results, changing it up only at the end (The prince visits a planet, etc). Second, I would include seemingly inconsequential details in the beginning and perhaps through the book that matter for the end of it, like Labyrinth's stuffed animals. If there's a cooler feeling to an eight year old than being in on the big secret, I don't know what it is.