Eventually you get to the five classes of plants.
4. gymnosperm (example -flowers)
5. angiosperm (example -pine trees)
A children's garden should be fenced (backyard fence is fine) for childs safety. A children's/family garden ideally should have three areas and reflect the world as much as possible. The first and immediate area should be of a hard surface like cement, second a cultivated part and third a wild part.
The concrete part close to the door or exit/entrance will help during times of mud or dampness. This may be a good place for storage too of all the garden tools.
The cultivated part could have plots for flowers, vegetables and fruit. Remember to make plots accessible to the child who will work with you in them. (height & width)
The wild part can be encouraged by favorite grasses, flowers, trees, slight hills and paths etc...
I just found this site with a large scale example of what is mentioned here: