Windows 8 has built in refresh and reset features.
Reset = the equivalent of formatting the PC and doing a fresh install of Windows 8, so you lose everything but are back to a nice fresh install.
Refresh = resets Windows 8 so it's like a fresh install, but it keeps your personal data and Metro apps.
So if your folks mess up the PC you have a couple of options there you could use, rather than doing the traditional boot from install CD - format - fresh install.
Also, I installed Windows 8 Pro on a laptop using the upgrade version and then I used an install CD I'd made to boot from, format the drive, the reinstall Windows 8 Pro again and it worked fine. I think it just checks to see if there's a qualifying version of Windows on the drive already, and if Windows 8 is already on there, that counts - it worked for me anyway.
Another, better option (IMO) is to get the laptop set up for your parents exactly how they want it, with all software installed, settings tweaked etc., then create an image of the drive using the free version of Macrium Reflect. If something goes drastically wrong you can use that image to go back to the exact state the laptop was in when the image was made. In fact, you can create a custom refresh image in Windows 8 itself to do that if you like.
You have several options anyway!
Thanks, I forgot about the Refresh/Reset function.
About the image, every time I reinstall a system (whether it's on my laptop, or on my parents' PC) I think about doing a system image, but each time I forget about it. Maybe this time I will finally do this.