Since my son was a very toddler we've enjoyed baking together. To begin with I made biscuits myself for him to decorate, then little by little I introduced him to more of the process.
When baking with very young toddlers than are still unsteady on their feet, it's a good idea to bring everything down to their height. I used to bring our plastic toddler table into the kitchen for him to work at. For a slightly older toddler I think that something like a FunPod is brilliant. It's like a stool for a child to stand on, but with solid walls on each side so that they can't possibly fall out.
Toddlers love having their own baking utensils. We purchased a nice set from Ikea but there are loads available. It's a great thing to add to a child's Christmas or Birthday list, and similarly it's nice for them to have their own child sized apron.
Choose a simple recipe which you have baked before and know won't take too long. We like to make basic shortbread biscuits and fairy cakes. These are particularly good because they are a two part process - you can first make them, and then later on you have the fun of decorating them!
I measure out each ingredient into a smaller bowl and then let the toddler tip them into the main bowl for mixing. Although I have a mixer, if we have time we often mix by hand as it's much more fun for the toddler. You just have to learn not to be too fussy if ingredients end up on the counter or floor instead of the bowl!
I try to wash up as I go along to avoid too much mess at the end. It helps to have a washing up bowl full of soapy water to dump utensils into, and I often also fill up the bathroom sink with soapy water ready for carrying a sticky toddler to wash hands.
Obviously there are dangers to watch for in the kitchen so you need to be aware of what your toddler is doing, and never leave them unattended. In particular you need to watch for hot things and sharp things, and make sure that if they are standing on a chair or similar that they are safe and cannot fall.
When your baked treats are ready you can enjoy eating them together, perhaps even saving some for family members and other visitors!
Below I've collected together some baking accessories that will make cooking with your toddler even more fun! (Affiliate links)