In school, we have an edible garden where children grow herbs, fruit and vegetables. They use these to cook with in their PPA sessions!
Growing your own vegetables helps children understand where food comes from as well as encouraging them to try different foods.
If you are new to growing vegetables, the easiest things to grow are cress seeds on some damp kitchen roll on the kitchen window sill. If you are feeling more adventurous, let some seeds from the fruit or veg that you eat dry out and then try planting them in soil to see if they grow. Tomatoes, peppers and chillies all work well like this.