My situation is a little different as I still live with my parents. I may not hide the fabric very well, but *I* might hide! Haha. Usually though (with my mother, at least) if I just show her all of it she can't deny how neat or pretty it is. And I'll just start talking a million miles per hour in "sewing" speak about how I'll just make this with it, and selvedge edge this and that and seam allowances and mitered corners and people get so confused and think I'm an expert and just go "oh, ok."
Just talk them in circles.
I also have a thing for vintage sewing machines and there really isn't much to do to hide those, particularly when they're in a cabinet. Though I see my mother is starting to get the "bug" too. I showed her a particularly neat looking machine the other day and she exclaimed "Wow!" and how neat looking it was and on and on. As the spider weaves its web...