Alexander Zvonkin's book is worthwhile both for math pedagogy and Soviet insight... the OP doesn't link the full book... either http://www.ams.org/bookstore-getitem/item=MCL-5 or http://www.amazon.com/Math-Three-Seven-Mathematical-Preschoo... is a great example of a preschool Math Circle.

If math pedagogy is your main interest any of the MSRI Math Circle Library books are worthwhile. This includes "Circle in a Box" which is a Math Circle starter kit freely available here http://www.mathcircles.org/GettingStartedForNewOrganizers_Wh...