You can run 2 antivirus, but it will conflict your system and cause problems. I just did this exact same thing with my Mom.....exact.
I moved her to AVG and then deleted McAfee. It asked me if I had another program running -well yes, did I know it,,,,,mmmmhhhmm, it's just a built in safety to keep their product. Download AVG today and delete Mcafee. Then restart your computer.