Paint a Greek Vase
If you need an art project, or something you can do sitting down, here's a suggestion for a good quiet project.
There are two main styles in Greek vase painting - black figure and red figure. Mostly before about 530 BC people painted in black figure, and after that time people gradually began to paint in red figure.
Black figure is called black because the people (the figures) are black, and the background is red. In red figure, on the other hand, the people are red, and the background is black. (More about black figure and red figure).
You might have your class draw first a black-figure picture and then a red-figure picture and discuss what the differences were between them. (for instance, it's easier to draw in black-figure because you don't have to color in the whole background, but in red-figure it's easier to show the expression on somebody's face, or her muscles).
Ancient Greece!: 40 Hands-On Activities to Experience This Wondrous Age (Kaleidoscope Kids), by Avery Hart, Paul Mantell, and Michael P. Kline (1999). Gives ideas to get kids thinking, rather than step-by-step instructions.