In ground, lots of fertilizer and water. Protecting one plant from critters should be easy. cover from the get go with a little tent made from row cover or tulle over a frame made from a tomato cage or sticks staked down all around to prevent the cabbage butterflies from laying eggs on the plant.
best of luck. Cabbage is a weird plant to give to children and its not super easy to grow due to pests mostly but sure worth a try
Maybe have some green beans or sunflowers as backups so she has some success
KarenO