Blow paintings are fun and easy!
Printer paper works better than construction paper for this project because it doesn't absorb as quicky.
Lots of kids will tend to suck instead of blow at least once by accident (it's a straw after all!) so food coloring is better than paint here. To reinforce the concept of "blowing," you can have them practice feeling the air against their hands first, or blowing a little ball of tissue across the table.
Using small cups or a muffin tin, make several different colors of nontoxic dye out of about 1/4 cup water and a lot of food coloring. You'll want it to be pretty concentrated so the color shows up.
Lay down newspaper or do this project inside a baking dish. Giving each kid his or her own straw and having a rinse cup to use in between, use the finger-over-the-tip method to transport one drop of the dye onto a piece of paper. Blow into the end and watch the color splatter across the paper. Super cool! Try adding different colors and going in different directions. Try mixing colors! The kids can leave this paper as is, or use it to make stationary, wrapping paper, paper collages, or a million other things.
Remember to take "Regular Breathing Breaks" so no one gets light-headed!