Since his General computer knowledge is beginner I think its a Good idea for him to have a antivirus on Linux
you could also checkout comodo antivirus for Linux if you are not happy with ClamAv
anyways if you are not going to the dark corners of the internet all the time then you are quite protected
I am a novice Linux user, I always had Windows.
Lubuntu is safe. ClamAV is often wrong and can not detect real viruses.
I use Chromium. The addition of McAfee URL Shortener helps me block a suspicious site. All right.
In Firefox I have added BitDefender