Gentle Posters; a book which I treasure, and refer to frequently, is the 'Ashley Book of Knots.'
It, combined with several lengths of suitable tying rope or cord, is one of the best child and adult diversionary devices in existance. There are over 3,000 different knots in this book, along with history of knots, trick ways of trying knots, knots particular to crafts, knots used in magic tricks, etc. In short, a vast amount of data, presented in an interesting, chatty format, well organized, and FUN. It is an absolutely must-have book.
Take it with you on the next time you know you will be sequestered with children for any time over 10 minutes. You will end up treasuring it as much as I do. Walt