Most children like to have a productive garden but it is essential that the fruits and vegetables they grow are varieties they are likely to eat. For example, radishes give satisfyingly fast results, but very few children enjoy eating them.
Some vegies that are popular with kids are sweet corn, cherry tomatoes, beans straight off the plant (not cooked) and snow peas.
Easy-to-grow fruits include strawberries (which can even be grown in a hanging basket), citrus trees of most kinds (especially mandarins), blueberries, passionfruit, and raspberries in colder climates.
Productive plants need a sunny position, compost-enriched soil (or potting mix), and regular watering and fertilising.
This information is from the Yates Garden Guide: fully revised & updated 44th edition, HarperCollins, $39.99. You can have this information and so much more at your fingertips by purchasing the Yates Garden Guide, available at all leading bookstores and Bunnings stores.