Is this software appropriate for illustrating children's books?
Yes, the software can be used for illustrating children's books, but it appears that you can obtain it only through the Sony Creative website that is listed below. While it can be a little expensive, I also recommend checking other applications from the same category.
You can also try the following apps that can be used to create cartoons and illustrations: http://software.informer.com/search/cartoon+creator
Sony Creative website: http://www.sonycreativesoftware.com/newbluepaintblends