I think you've misread the article you're linking to. All the article said is that it download ~5gb into a folder as part of the update. And leaves it there. Does nothing with it unless the user specifically chooses to click the "upgrade" button.
Your family aren't being guinea pigs. The worst they'll get is ~5gb less space on their hard disks. Heck, they've probably got more than that in their recycle bin and system restore points and so on. Totally not worth investing your time to prevent this.