I had this posted in the old forum, but I thought it'd be worth it to re-post it here.
There is a trilogy from Terry Brooks (The; Shannara series and; The Void and the Word series) that bridge the gap between the two. The trilogy is called; The Genesis of Shannara with each book titled; Armageddon's Children; The Elves of Cintra and; The Gypsy Morph.
The very first book you could drop into Kidworld and use it as a series of modules. It even has a kid in a wheelchair, and characters that range from young to just about to join the adult world.
If you ever have the time these books are a good read, even if you never intend on using the ideas for Kidworld.
You do not need to get any of the other series to understand what is going on in this trilogy as it is a pretty much stand alone series. It is written with the other series, in mind, that was written before and after.
If your right eye causes you to sin, tear it out and throw it away. For it is better that you lose one of your members than that your whole body be thrown into hell.
They're not really books themselves, but several of the stories in the anthology "Shadow Show" (a collection of science fiction stories by various authors inspired by Bradbury) definitely gave me a KidWorld vibe. I don't remember which ones exactly those were, though... If I find the book, I'll try to look their names up.
One is about an old woman living in a post-nuclear war world who finds one day an advanced machine from before the war which shows holograms of her dreams, and it creates children for her to tell stories to (it's a very heartwarming story).
Another one (and far more "KidWorld" in feeling) is about a future in which kids worldwide have begun for some mysterious reason to transform into bloodthirsty animals, and features and adult driving an extremely rare "kid who still thinks like a human" across the dangerous country to a research facility...