I have a 10 and 13 year old daughter. To get them more involved in healthy eating and cooking, I have them each plan a meal a week. They make the shopping list, help me pick the food out and then do most (if not all) of the cooking. It's been a great experience for them, and they are really proud of their accomplishments and all the praise they get.
Tonight, my little one made roasted carrots, parsnips and brussels sprouts to go with the tilapia she wanted to make!