A friend is concerned that her daughter may already be getting the wrong message about math and gender in kindergarten. This is not as far-fetched as it seems, according to this article.
She is planning to start a math club of sorts for her daughter and her friends.
My advice to her: do whatever math you think is fun to do with those kids -- mental arithmetic, geometric puzzles, non-competitive versions of the game Set (e.g. making "one-difference trains"), seeing what happens to drawings when a mirror is placed on them, the game of buzz (which must be known under many names), making designs with pattern blocks... But avoid any math that you yourself do not think is fun, as that would undermine the whole project.