Proper Shutdown of SQL Servers in a Cluster
Does anyone see any issues with that?


You are correct in the steps but your approach is way too much for a little work. 

For disk maintenance, why would you shutdown the entire cluster ?

Just suspend that disk (which requires maintenance) and then once it is done resume the node.

Basically, SHUT DOWN CLUSTER will stop all the roles and services on all the nodes of the cluster. The Cluster UI will ensure that all the roles and services are shutdown gracefully.

Seems like you have posted the same question at SQLServerCentral.com

Refer to How to Properly Shutdown a Failover Cluster or a Node