omgosh I love that article as well. Even DH thought it was an awesome idea when I made him read it. I still have that issue...well somewhere here

On the whole food idea Im ususually not a waste food type person either but I have found that some food items like a 10 lb sack of flour are not only easier to clean up but a little safer to use than say flying sand in eyes.
I wait until it really warms up outside and tell guest to come in their bathing suits that way we can have a sprinkler going that they can "clean off" in before they go home or inside my house

some of the "hits" have been:
making gak/slime
painting. we have huge buther paper we clip to the fence and the kids go nuts with paints/stamps/rollers
we have a small sand box
kiddie pool with 10lbs of flour in it and lots of dump trucks and various plastic kitchen utensils
some type of food decorating like frosting cupcakes or cookies with tubes of icing which double as a snack