I wouldn't bother with antivirus on the Mac side--not until actual Mac virus threats exist. Which will make headlines, so you won't miss the news
(Actually that headline has ALREADY appeared about once a year--a false alarm with a tiny retraction on page 999 two months later.)
The Windows side is what needs virus (and other malware) protection. I did a lot of research and found people consistently recommending the same set of free anti-malware apps:
Spybot Search & Detroy
So those are what I run in WMware. On the Mac side, nothing except the built-in firewall.
Virtualization (VMware etc.) DOES provide some virus protection by its nature. For instance, a Windows virus on VMWare can't touch your Mac data (unless you intentionally share the Mac volume with Windows--which I do not do). But a Windows virus can still attack the Windows side, so stay safe!