It may be relevant to note that http://wikijunior.org currently redirects to http://en.wikibooks.org/wiki/Wikijunior .
From what I've heard, Wikijunior was supposed to become its own separate
project at some point. Now, that is Wikibooks-related and not Wikipedia-related, but if one were looking for a combined edition of all the projects in each language, for children, you've got the domain name there, owned by Wikimedia.
-- Aaron Adrignola