John, Macromedia Contribute 3 works quite well if the templates the client is to maintain has a relatively easy structure (which would be the case with your sites where accessibility is a top priority).
I attended a Macromedia presentation of Contribute 3 a few months ago, and was quite convinced that that was a good alternative for the client to maintain their site, instead of a custombuilt CMS, which ultimately would be too expensive for the client if they're on a budget.
I have a few clients using Contribute now, and they are extremely happy with it.
Read more, and why not download a trial?
http://www.macromedia.com/software/contribute/