Not to hard to do, and unless they are computer savvy they will not figure it out.
Since GMail and Google+ both operate on their own subdomains so you can block them via the hosts file.
Open Terminal and enter:
Code:
sudo nano /private/etc/hosts
Now add these two lines at the very bottom. You use the arrow keys to navigate.
The space between the IP and the domain name is a tab when you enter it.
127.0.0.1 plus.google.com
127.0.0.1 mail.google.com
To save changes: control+o then control+m
To exit: control+x
Then run this to make the rules active.
Code:
sudo dscacheutil -flushcache
Now when someone tries to load plus.google.com, the system will check this file first, see that it needs to be redirected to 127.0.0.1 which is a loopback IP and error out because it can't find the server.