This is a great approach for children even if they are not directly involved in bitcoin at their current age. But at least it creates a bit of awareness through intent to read, draw or color even if they don't understand how it works. I don't know what you want to give a surprise like this for, but for sure it's great for kids because most of them like to paint, draw and color whenever they see something unique and interesting for them. For an initial introduction to bitcoin I think this method is more effective because drawing and coloring are their world.

Have you ever gone to a bookstore and looked at the availability of a comic or novel that includes pictures, coloring and discussion of bitcoins in it because I think for now it's available for bookstores in urban areas. You can also visit online stores and there are several people with drawing jobs who often sell their work in the form of comics and novels in existing online stores.