Paul, actually your life just got a LOT simpler - Macromedia's Contribute could be just the ticket. Available now for Mac OS X or for PC's, it is supposed to be as easy as using a word processing program. The web master retains control - sets the area of the page that is editable by others, hands out a password, and then the user with the password can update the pages at will - text, photos, etc. It is VERY cool. I'm hoping to get our school system using it soon - I just downloaded the trial version of 2.0 for Mac yesterday (it just came out yesterday!!) You can use it in conjunction with sites designed on DreamWeaver, GoLive, FrontPage etc.
It is also MUCH MUCH more reasonable cost-wise than any other content management software I've seen - $99 for a single copy, with other various prices for education, multiple users etc.
Check it out:
http://www.macromedia.com/software/contribute/Iain's methods are also good, but require a bit more knowledge on both ends, I think. Contribute makes it very easy.