How can I easily setup and maintain multiple user accounts who need access to the web directory used by Apache?

This single directory (with subdirectories) contains sample files for users to download and they are maintained by a handful of users who should have r/w access and the ability to create folders and overwrite eachother’s files.

They should not have access beyond their ability to manage these files as described above. These users know how to use FTP that shouldn’t be an issue.

What is the best way to set this up?