As I understand it, MM's Contribute allows users to write their own content once a site has already been layed out. Think of it as a template system that allows users to upload new content, thereby making it 'psuedo-dynamic' in the sense that the site gets updated everytime the client wants to say something new.
However, it is not truly dynamic in a web developer's definition of the word, as it does not allow for adding, changing or deleting info in the db. What happens is that content on the htm pages, or even php pages are updated with new text, images, etc. You can even create new pages with it. But it doesn't interact with a db directly.
For that, you will need the php / mySql combo.
PHP / MySQL together can do exactly what your clients need. You will be implementing a CRUD system (Create, Retrieve, Update and Delete).
Have you ever created a DB, tables in the DB, and connected to it via a .php web page?
If not, there are plenty of tutorials online. (I started with this one and this one [but there are plenty of others] ).
In my opinion, you will get more bang for your buck if you look beyond Contribute, and do things the truly dynamic way with php/mysql.