Controlled shutdown/startup of a cluster
Shutting down the cluster for a move is pretty straight forward.


Open the failover cluster administrator.
Using the failover cluster administrator stop the resource groups for the SQL instances
Shut down two of the nodes.
At this point the cluster will fail and the cluster service will stop.
Shutdown the final node


To bring things back online.


Startup all the servers.
Start the cluster service if it didn't start automatically
Verify that the servers can see the storage correctly.
Startup the resource groups that host the SQL instances from within the Failover cluster administrator assigning them to the correct node of the cluster as you start them.


A word of advice, make sure that EVERY cable is properly labeled at both ends before you unplug anything. I've done this kind of move a few times.  A couple of hours of labeling the cables will save you hours of pain when getting things back up and running.