Dear Jayden,
may I ask just how computer savvy the others are at your son's house? Having said that, I'll say that I'm (at best) only computer semi-literate. As far as technical stuff goes, I'm clueless. However, my experience indicates that, in general, it isn't the game that poses a risk to the computer, be its functioning or in terms of viruses.
If I'm understanding my experience correctly, you COULD have issues affecting the computer if the graphics card isn't up to the specifications needed to run the game or if things aren't configured correctly (drivers and such).
I, personally, have had issues running CoX on Vista ... I was distinctly worried that whatever imcompatibility there might be, would burn out my graphics card. I switched back to XP and don't have a problem. That being said, I understand that not everyone has problems with Vista and CoX (or, any other games).
I'm sure that there are many others that can and will address technical issues connected to CoX, if that's a concern.
As for viruses and such ... again, in my experience, it isn't the game itself that poses the risk. It is much more likely to be injudicious internet browsing. May I ask what what internet browser is used in the household. I STRONGLY recommend against using Internet Explorer. It is my understanding that it is not a really safe browser. I DO recommend Mozilla Firefox ... and it has addons that make it even safer; one that I use is NoScript ... it prevents any nasties from being able to alter/rewrite anything on your machine ... unless you specifically give it the ability to do so. You actually need to do this by using a menu ... you can give permissions temporarily or permanently. I mostly just give the permission temporarily whenever I visit any given site. It's a bit fiddley to do it everytime, but it's worth it for me.
It's also a good idea to be VERY careful about what you click on when you're visiting sites like the various internet forums you'll find on the net. 99.9% of linked images and such are probably perfectly safe. However, it only takes one bad link to cause problems. In fact, it is entirely possible (this happened to me earlier this year, which is why I now use NoScript and AdBlock) that a perfectly innocent link is provided to another site, that is also perfectly innocent EXCEPT that someone has hit it with a trojan or malicious virus and corrupted that perfectly innocent, non-malicious site ... and the owners of that second site may not, as yet, even be aware of what's happened.
I'm certainly willing to attest to the integrity of the game and the fun I've had. Also, the great people I've met and played with in the several years that I've been here.
I, also, feel that for parents and children to play together as a way of interaction is an enormously valuable commodity. I play (mostly pen and paper, tabletop) games with my twenty seven year old son. We've been playing them together, on a regular basis, since he was about fourteen. I feel that it has added immeasurably to our relationship. In fact, it was my son who introduced me to CoX when I was down with an Achilles tendon injury. Sadly,he's not playing CoX at the moment; he's gone back to WoW, which I've also played, but am allowing to languish, for now, in favor of CoX; a situation that has continued for almost three years. I choose CoX for any number of reasons ... community, the fact that as a game it's not nearly so loot driven among them.
I don't know if any of my ramblings have addressed any of your concerns but here's hoping! And I hope that you can reach an amicable arrangement with the powers that be in the household where your son lives.
Geni