Yes, it will be very messy but from 18 months old, your superstars can help you with cooking and baking.
First of all, make sure you get or selfbuild one of those kitchen helper tower, to get your child standing safely, it is easier for them to help out standing instead of seating in their highchair.
Mixing bowls, spoons etc WILL fly, it comes with the territory! Don’t be afraid of the mess, you will clean later, it doesn’t matter, it is fun for them and that’s the most important, it is a quality moment.
As far as recipes, the world is your oyster. I would say baking is the simplest to start with as it’s about pouring and mixing. Make sure you talk about what you are using and doing, it is a good time to improve their vocabulary.
Internet is full of ideas so go crazy!
But keep in mind to prep as much as possible so you are always within arm reach of your child and you are not using the stove,sharp knifes or the oven with them nearby. Safety first always.