I have a friend who wants to use WordPress as a CMS for their company website. The owners of the business dont know anything about HTML so they figure if I set up all the required pages, they can maintain each page through the WordPress Dashboard in Visual Edit mode.

The thing is, "Visual Mode" is not quite a true WYSIWYG. For example in the visual editor you don`t get a true sense of where images will end up on the page.

Does anyone have any advice about how to make WordPress an easy CMS for my friends to use?

Using wordpress like an CMS is not so bad idea. Already got 3 projects that using wordpress. You can make an search in Google with your topic sentence and you'll find lot of tutorials in the web where can collect the main points where to start.
Yes, probably will find some unpleasing things (like WYGIWYS editor) but nothing comes easy - this is not so big deal.
For me the main problem is the security of Wordpress , nealy every two weeks there's a new version and the main reasons are security fixes, so - have to secure your site.