Options to enable support for multiple content contributors

Hi fellow DreamHosters,

I need help identifying options to make an informed decision as to whether or not/how to enable other people to help create/maintain content–on a static site.

My web site is a special interest site that is over 10 years old and enjoys good search engine ranking. The site has over 200 articles (static, standards-compliant HTML pages) and a lively PHP-MySQL-driven forum. Site design is controlled by CSS; shared elements are managed by SSI.

Most of the articles on my site do not need updating (phew!); however, a small number of reference pages requires on-going maintenance, and there is a growing demand for new reference guides to be made available.

I am receiving more article submissions from enthusiastic site supporters than I have time to add to the site (i.e., transfer submitted content to HTML, update any affected index pages, and then upload new/modified files). So, the question is how best to manage this situation?

What safe options do I have to allow a select few non-technical volunteers to help with content generation/maintenance? Port the HTML pages to a Wiki? Convert site to WordPress? Or don’t change a thing - problem lies with me, so I should just work harder!?

Would moving the site to a Wiki or a CMS be more trouble than it’s worth? Would such a move break all existing URLs and damage my site’s search engine ranking? Also, I do not know how installing a new system in the root directory would affect the discussion forum (currently installed in a subdirectory) - the most popular section of my site?

Any suggestions/advice will be gratefully received.