Turn alerts off on the PCs that you don't want alerts showing on:
- right click the connector system tray icon
- deselect Display Network Health Notifications
On a computer you've done this on, the system tray icon will always show either Green (if the server is detected on the local network) or Grey (if not).
Regarding McAfee, in the console you can choose to ignore that notification. Then you won't be reminded any more.
I'm not on the WHS team, I just post a lot. :)