My advice for baking with a toddler.....
Do allow him to "wash the dishes" alongside you, while you set up. Be sure to throw more dishes in. Even clean ones. Anything within reach will do.
Do allow him to sample the sugars and the chocolate chips. Try to avoid the flour, even if he insists.
Do allow him to pour the ingredients into the bowl. Dodge his attempts to pour soapy water into the mix.
Don't stomp on the old old bag of brown sugar to break up the brick-like pieces inside. He may get excited when he sees your dance and toss a cup of water in the air with an "Ole!" finesse, since this looks like a party to him.
Do allow him to eat only a few bites of his dinner. Then allow him to climb into your lap and stuff himself with an adult size just-off-the-cooling rack cookie. He is only young once.