If the PC's will have internet access , try Panda Cloud Antivirus (Pro) , I am using the free one and it's very good . In online mode , NO other antivirus can have as exhaustive a definition database as it has .
Alternatively , if you want a non cloud one , then I'd recommend Microsoft Security Essentials (If the PC's have genuine windows , its free and very decent) .
ESET is also very good . I tried the latest versions of KIS and Bitdefender (there were some free key giveaways) and found both way too bloated
P.S. - Stay away from quickheal