SQL Server 2008 R2 - Moving nodes in mirrored environment
You are correct..


Install SQL Server on the new nodes
Use SP_HELP_REVLOGIN to copy the user account to the secondary node
Take a full backup and a single log backup of the primary server and restore on the secondary with no_recovery
Break the mirror and remove the secondaries from the primary server
Create the endpoints with TSQL or use the Mirroring wizard to configure them and endpoint security
start mirroring