Seven-Day Magic

Seven-Day Magic (Tales of Magic Book 7) by Edward Eager illustrated by N. M. Bodecker

Kids are living their life. Then they are part of a story. But is the story still being written? They end up with a book that grants wishes. There are some crazy adventures, like a baby that ends up driving a train. In the end, one child wants to help their dad get the singing fame he deserves. Thing take a few turns. First his solo ends up getting him fired. However, people like what he did and now he gets many job opportunities - as a novelty singer. However, they later run into a poet who is working on an artistic play and would like him to do it. This gives him the chance of fame while preserving identity.

After theis adventure, they contemplate, keeping the book out past the one week due date. However, after deciding to do that, bad things happen. They have gone against the book and it did not like that. 

The book has a humorous take on magic. People are both living in the magic world and seeing stories about it.