I *love* the idea of storybook creation.
Here's my add-on: dear students, you decide what product you want to build. I have some instructions for the activity here
https://kasperowski.com/experience-agile/. In previous classes, people have created books for adults (yay!), children's storybooks, slide decks for their company, a video series, board games, TV game shows, Agile beer-pong, a live-action adventure experience, and the best one ever: a full-fledged hip hop opera - delivered with a full performance.