That's probably not a good reason to quell curiosity and experimentation. The other day, I decided to let him try, with the caveat that he make a small batch. Here's how it went:
Vincent's Peanut Butter Chip Banana Cookies with commentary and handy tips from V
In the wet bowl:
1 egg (whisk)
1/8 cup oil ("hold the cup upside down a little bit; oil takes a while to come out"
1/8 cup milk
1 banana (he asks me to slice; he then smashes with the whisk)
V: Why don't we make a recipe store here if my cookies turn out good?
In the dry bowl:
1 cup flour
1 tsp sugar (for next time, he suggests a tablespoon)
1 tsp salt (I said no to this amount)
2 tsp baking powder
1/2 cup peanut butter chips
V: Shouldn't we write what they taste like? They taste like artificial banana flavouring with cookie dough and a little bit of sugar.
V: I'm proud. I enjoyed making them, but I'm not going to enjoy the dishes.
I was very impressed that he'd remembered to separate wet and dry ingredients and had remembered all of the major components to most baked goods. He also chose fairly accurate measuring cup and spoon sizes for the ingredients. The cookies tasted a bit biscuit-like but definitely edible.