I did this with my second grades and they had a blast! Once we went over the severe consequences of playing with the straws and paint, we settled down and had fun. I used watered- down tempera in analogous colors for each table. Then gave very specific instructions on how to use the straw to blow the paint around the paper. While the paintings dried, I gave each child 4 small squares of colored construction paper. They had to have eyes and a mouth, but they could use the scraps to add whatever they wanted.
This was a quick, easy, and fun project that was finished in just one class!