Another good plant for kids is
Stevia (Stevia rebaudiana) - they really like to nibble on the leaves. You might even try to make some lemonade with the stevia they have grown and real lemons for a sugar-free healthy beverage (experiment at home first so your juice has the right sweetness). Stevia is not hardy over winter so you'd likely need to get it going inside during early spring so it would have enough bulk to it before school is out.