Kids are often eager to help. It's a great way for them to learn while still getting done what you need to get done. Cooking is one thing that is good for kids to help with. The problem is that the kitchen and cooking involve dangerous tools and equipment. Always watch children in the kitchen. During a Home Inspection I often inspect for defects but some safety items are checked. Somethings I check are water temperature, electrical hazards, GFCI outlets, and anti tip brackets for the range. Do your own safety check before letting a child in the kitchen.
A list of kitchen tasks that various ages of children can do was put together by the National Fire Protection Association. You can get it here http://www.sparky.org/parentpage/pdf/Cooking%20and%20kids.pdf