Hello,
Well, if you just want to stop the failover for manual reboots, then yes persistent freeze is your answer.... so offline group, persistent freeze it for cluster & then reboot your box.... Also make sure it is persistent freeze only.....
In case you tune any parameters like "Autofailover" or "autoevacuate" then cluster behaviour will change for both manual reboot & system crashes, so this will not be suited to your requirement right now....
Hope this clears your confusion.... :)
Gaurav