Hosting files for clients to access

Hey i just have a quick question about setting up a shared folder for people to access securely. I run a freelance media company, and one of my main clients is the University of Victoria rowing team. i want to create an easy way for me give clips to the team, while hosting them on my DS1621+ NAS. The system i currently have is that i made them a login, with only read privileges for the shared folder i put their videos in. this works well, but because everyone on the team wants to login and access them, and share with their families and friends, im gewtting a bunch of connections from random ips. Is there a way were can set up a Geolocated IP lock, were only people in victoria could access my NAS. Or is there a more secure way for me to get these files to the guys.

Best,

Alex