This activity is suitable for any age
There is much research supporting the simple coloring of a pre-drawn mandala produces significant relaxation in school-age children.
The following links will provide you with a free download:
In the left column near the bottom under the heading "Advanced Coloring" click on "Mandalas"
Go to almost the bottom of the page and click on "Free Download: Starwood designs to color in"
Print out mandalas and have children color them in with colored pencils.