My wife and her friend wrote, and are hoping to publish, a children's book Funville Adventures. Children as young as 5 will enjoy the story and math-rich play; older children and adults can also investigate the deeper mathematical concepts!
Here's the link to the Kickstarter campaign
https://www.kickstarter.com/projects/419899136/funville-adventures-a-math-inspired-childrens-book Please consider backing the campaign and help spread the word!