You may want to look into a content management system (CMS) that can be loaded onto their server. I am not sure of your skill set but it uses PHP, CSS and MySQL (or other database) and is very easy to manipulate for the user once set up. Of course it can be complicated as well so do your homework and find a nice easy one for them. Here are a couple links to get you started and the good thing is that they are open source applications.
http://www.mamboserver.com/
http://www.joomla.org/
http://drupal.org/
Take care.