You should explore Clinked as it sounds like what you might be looking for.
Clinked's software all comes with it's SmartSync software where you can share a whole folder with other software users simply by right clicking on the folder and typing there name. It's as simple as that. It even saves the people you've recently/frequently shared with- so potentially you could share your folder in two clicks.
Clinked offers three main products- I would suggest the SmartDrive product. It's easy to use (especially with the SmartSync software) and has so much more than many other brands.
Have a look at http://clinked.com/site/clinked-smartdrive/
and see if it would suit your client's needs.
If you need any more help, I actually work at Clinked so feel free to private message me!