For reference information such as a Glossary, the wiki would be better to use as it can be kept up to date as a living document regardless of how often it is updated. If kept in the forum, users may have to wade through several posts as updates are made to it. And, when edits are made, it will show up in the New Posts result list which is probably something you don't want since users won't know what edits were made.

You may want to consider limiting editing to mods or volunteers. This would hopefully limit your administration duties. Suggestions for input into the wiki can be done through the forum. The Aneros community has recently done something like this and it may work here as well.

Onthepath