DNN should be an excellent fit based on the requirements you give.  It provides excellent content management features and an authorization model for who can add/edit that content etc that sounds as though it would fit your needs.  The out of the box benefits I see in your case are as follows:

1. A simpler CMS solution - many end content providers find Front Page and all it's options daunting when all they want to put snappy fresh content out there in creative formats.  Donn's WYSIWYG editor out of the box is good and much simpler than front page and there are others should you need a bit more horsepower (for instance the telerik Text editor at www.telerik.com).  This means all staff in charge of content can use a single simple approach to CMS.
2. The content itself is stored in SQL making maintenance (back ups, etc) easier to handle.  Not thousands of separate html files and their required/linked resources spread all over or nested all over the place in some VSS implementation.  Given that they have a dev on site and also given some for thought on shred resources (images, etc) this approach is a good one.  Consider the ease of searching that content in the future vs indexing all of the sites for instance.  Would rather search a single table or set of tables in SQL vs index loads of various sites spread all over.
3. The ability of DNN to host multiple portal instances gives one common framework for working with content across several disparate brands/sites allowing the subject matter experts to focus on the branding, presentation, and content rather than trying to re invent the wheel and find a better solution the next time they choose to launch a new site.  Definitely look into this feature.  Couple it with the ability to hold the content from multiple sites as portal instances in a single back end store and the benefits multiply...and hey if for some reason you need a different physical db to drive a given site that is easy to implement as well - transparently to the end users.

  The benefits compound  even more but these three should be sweet spots for the "need" you are describing.  I also advise getting the help of a good developer familiar with DNN if you have not worked with it before.  It is like any other powerful technology - you can do amazing things and that can be easily abused especially over time and lead to later unforeseen costs/side effects that fall into the category of "lessons learned" and a good experienced professional can help avoid these pitfalls.

Good Luck and keep us posted,

Hutch