The coffee table top is GONNA get ruined anyways! :) Repaint a coffee table with chalk board paint. Draw a road, game boards, self portraits, work out homework problems, or just let the kids go wild. It will keep them entertained for hours.
Popped Bubble Art: Simply color bubble mix with food coloring and blow bubbles onto paper. As the bubbles land and pop, they create beautiful works of art. A great kids activity for those lazy summer afternoons