Is there any way to see timestamp of when uses are activating / deactivating themselves in queues they are members of?  for auditing purposes our supervisory team is asking for this informaiton.   Any API calls or views where this is available? 

The Audit viewer, using the Contact Center service, will show you users join/unjoin events against queues.  So you could then use the Audit API to run something separate if you need that in another format.