The easiest thing would be to migrate the wiki from Mediawiki to TiddlyWiki
While I'm a *huge* fan of TiddlyWiki, I have to advise caution here: TiddlyWiki is a single, JavaScript-enabled HTML file, which also contains all contents. Due to this single-file approach, there are limits to how much content should be put into a single TiddlyWiki file. TiddlyWikis are measured in KB (there is no fixed max. size, but anything above a couple of MB will probably cause problems). MediaWiki wikis, in contrast, are usually measured in tens or hundreds of MB - way beyond what TiddlyWiki can or should handle.
-- F.