I wonder if you have investigated enough concerning the products you mentioned. While VirusScan can be run on each indiviual computer, whether managed or unmanaged, ePO is a management system that you run on one single server (including database), which manages all machines in your environment. It is a powerful tool that is capable of managing far more than simple virus scanning.
Running ePO in your environment will likely "cost" you a full-time employee. If you simply want to have users run an AV program on their PCs, then either install McAfee's VirusScan in unmanaged mode, or choose a different stand-alone virus program.