I saw the cutest idea in the book, Gardening Together with Children. Quote from the book: "You can design and grow you dream house with just a handful of sunflower and morning glory seeds, some sunny ground, and water. Shaggy green walls topped with gold and russet floweres will enclose the perfect playhouse for tea parties, picnics, or quiet moments together. The slender tendrils of the morning glories will twine their way up the sunflower stalks and form a lacy roof. The best days will be when you lie inside your house and look up at the heavenly blue morning glory sky and gient sunflower faces smiling down on you."
It is such a cute idea and the the book gives great directions. Another idea was a "Pizza Garden" The pieces of the garden each grow a pizza topping.
Anyway, I got the book from the library. I would reccomend checking it out.