Without oil, it will dry out very fast, without salt it will go funky quickly (salt preserves) Having said that, if you really want to have fun just use flour and water and add whatever takes your (and your child's ) fancy - peanut butter, milo, sultanas, powdered custard/drink mix/drinking chocolate, whatever. You can have a great time making up your own concoctions together and they can be eaten without worry. Don't use them more than once though. Also, if you use SR flour, you get stretchy dough. Essential oils are nice to add too, but I wouldn't recommend eating those. I have never found it necessary to add alum to dough - sounds kind of american. My recipe is very similar to blizz's so I won't bother posting it but if you buy the cream of tartare, there's a recipe on the box.
Have fun