Ship Full O'Pirates is stacking up advice, go take a look!
My kiddos have been helping in the kitchen since they were itty-bitty. They all love to cook and fight over it! This is one thing that helps me. It's actually a tiny excerpt from the forthcoming Large Family Logistics book (we're still working on editing).
Assign a day of the week to each child. The "special" child for the day gets extra privileges and is also Mama's right hand in the kitchen. By assigning each child a day in the kitchen they learn how to cook! My children love to cook and try to cook on days that aren’t “their day” and this often turns into a squabble! They often get excited about a recipe and are told to save it for their special day. Ingredients that they need are added to the grocery list.
The child assigned to the day is required to be in the kitchen during meal preparation. Involve the child in the recipe making and if they can, let them do it alone! Start this when they are little and by the time they are 8, 10, and definitely by age 12 they will be able to make meals alone!
Show no fear! When they want to make cream puffs and you think the recipe sounds too complicated, let them do it! Tell them to follow the directions of their recipes exactly. I tend to be a “dump cook” which is good and bad. The good is that a dump cook can make something out of nothing and no recipe. The bad is that a dump cook rewrites the directions to a recipe and can end up wrecking it. I have learned, the hard way, that when the kids want to make something that requires exaction—baked goods—and they have a reliable recipe, that I should get out of the way! If they see a recipe made on a TV cooking show, let them get the recipe off the internet and make it. Help them out with collecting the ingredients and being their dishwasher and the supporting role in the production. Then sit down and enjoy the food!