Following the NDU process (use upgrade advisor) you run cf takeover then giveback on each node (with a takeover -n after one node is upgraded to halt the lower system). All vFilers stay running. When a node takes over another node the partner runs an instance on that node along with all its vFilers. Just make sure all network interfaces have working partner interfaces and you are good to go. Also make sure all hosts have timeouts set properly (iSCSI, FCP - no fcp in vfilers though, NFS). CIFS will be terminated since not persistent with an Non-disruptive upgrade.
Run through upgrade advisor and review the plan... I also wonder why you are going to an RC release instead of staying on GA (8.0.2P6 for example)?