Kids and computers...
I have to respectfully differ with your assessment of "non parents". I'm not a parent of any children and very likely never will be. (Bear with me on this.) I do have to temper what I'm about to say--yes, I know not everyone is a computer technician. And far be it from me to tell *anyone* how to raise their kids, everyone has to make their own decisions there. Even so, what I'm about to say is offered with nothing more than the hope it will be useful or informative. Take it for what it's worth, the 'rantings' of some random commenting dummy on the 'net.
(Yes, I feel I can get away with making some of the suggestions here that I do, because I'm assuming things about The Register's readership and feel pretty safe in doing so.)
I do have younger brothers, and I felt it important that they have access to computer technology. This was back around the Windows 98 days, and both of them had old Compaq Deskpro/M 486 class machines, the idea being that if they tore up an old PC, nobody would be too upset. There were a few lessons had to be learned around this point about how to treat computer equipment with reasonable respect. Of course, Windows 98 has no meaningful security model, and this also led to some interesting experiences. One brother deleted the startup files from his computer and the other experienced what happens when you go pr0n surfing.
As time went on, they got newer computers and moved to newer operating systems. One got a Lenovo laptop (upgraded from Vista to XP) and the other a Deskpro EN P3 with Windows 2000. At that point, they both had limited rights accounts. I took other measures to be as sure as I could that no issues would break out--I talked with my brothers about how having a computer is both of a wonderful privilege and a huge responsibility, installed AV software, and enabled operating system resident security features (system-wide DEP in particular on XP), amongst other things.
Now, granted, having a limited rights account on Windows has always been something of an uphill battle, but it was one that I fought and managed to win. I got their games and software working. It wasn't my first go-round, most of you here will know what it's like to get some stupidly-coded line-of-business application working in a corporate environment without handing your users any remotely privileged user account.
These days, one of them has their own computer that they purchased with their own money. As such, they do have an admin-level account (because it's their box). Yet they have gained an understanding of the machine, its power and how to stay out of trouble with it. (Still, I did do the initial setup, because they requested that I do so, and I went through dotting all of the i's and crossing the t's.)
So you don't want to do that? Don't have the experience? As a freelance consultant, I've worked with parents who are interested in getting their children a computer, and one of the first things I always say is "make the computer a family experience and know what is going on". When they do, it does make a difference much of the time. When you're involved and know what is going on, a lot of problems really do disappear. Even if you do have technical experience, it's not a bad idea to make the computer a family experience and to provide some guidance along the way.