This is one of those fun art lessons where you can gather the materials together fairly quickly. This can be done with crayons, markers or watercolor paints. This can start as a doodle lesson and you can later come back and discuss the works of Cezanne. Really another beautiful opportunity to reinforce that everything we draw is a series of shapes.
Mark Rothko is another artist that inspires the use of simple shapes to create beautiful art. Here is one from my series - Enjoy!