The MediaWiki way is workable, but with manual
maintenance of namespace
prefixes or categories required, I have a bad feeling as the target
users do not have a technical background on the whole.
A simple approach of "be in the right place"
and "click new page" to get
an implicit hierarchy is probably what they are after, based on an
initial chat with them.
I find
http://www.mediawiki.org/wiki/Extension:CreateArticle quite useful.
Users get an input box for creating new pages which takes care of some naming conventions,
e.g. namespace. And you can easily add a template for the new page together with
intstructions on what to fill in where.