Keeping service up while taking drive offline in clustered instance
I've never tried this before but thinking this out logically, these are the things I would do (in no specific order):


To answer your question yes, exclude drive K as a dependency as a cluster resource (this should prevent it from causing the cluster to go down when you need to remove it) 
Manually take those databases offline that are stored on drive K
(I usually set the database to single user mode to make that happen)
Triple-check that nothing else is stored on drive K (like any text log files, etc) that may be used by SQL Server (make sure you dont have any hidden files too)
Take drive offline, rescind the space, then bring it back online