There is some good advice here except I have found that
like anything, there is no single tool that will protect
against everything. Also, if the computer isn't particularly
speedy to begin with, loading it up with all that stuff
might make the entire computing experience not so fun anymore.
I have been doing computer repair/maintenance for 13+ yrs now
(self employed) and I don't work IT in a big company,
I work in the field for small offices and home users just like you.
Yeah you can try to tell these kids not to click this or that but
in my experience it doesn't seem to help.
Some things I can recommend so that fewer pests get through:
Do not give the kid Administrator rights on the computer. They
can't do as much damage with a Limited User account, but they
can still use the internet, chat, facebook, email, listen to music, and do school work.
They won't be able to download/install crap like Limewire, Bearshare, etc.
or other programs that have the potential to bring trash in that can
cripple the machine.
Make sure latest Service packs are installed if using Windows.
Make sure your java packs are the the most recent.
Use Firefox web browser.
AVG Free antivirus is what I install for my clients, it works well
and it requires little to no manual intervention. Use the most
recent safe search add on. It really helps keep bogus web site
out of the search lists.
Spywareblaster - requires manual updating and implementing
the updates but it works well to keep pests out.
Spysweeper - not free. works very well but will bog down an already slow system
Malwarebytes - very good at removing adware/malware that got past the other stuff
Lastly, I give all my clients with children this link:
http://majorgeeks.com/
That site will help you keep up with the latest in antispyware/antivirus/etc.