how to resync standby's with primary db copies?

We have a scenario where the application is getting a major upgrade that will cascade many database changes to db's.  There is a very slight chance that it will fail and we will have to either restore from backup to before the upgrade or point the app to some copies of the primaries that will be created from before the upgrade.  My question is if we use rman to make duplicates of primary db's with different db_names/sid_names, and we shutdown the standby's before the upgrade and leave them down until we verify that the upgrade was a success or failure,