1 cup peanut butter
1 cup light Karo syrup
1 cup nonfat dry milk
1/4 cup powered sugar
I know this seems like lots of sugar, but it really doesn't taste too overly sweet. And it beats having to sit and watch your kids like a hawk so they don't ingest that nasty other play dough.
Have your kids help you measure and pour the ingredients into the bowl. You can also have them help you mix once you begin to knead by hand.