I'll say this, I personally am not a huge fan of telling people about this. The way I look at it, once you tell, you can't take it back. Sure, there's plenty of people on this board who have told their parents, some with good results, some not.
As for me, well I haven't lived home for several years now so it doesn't matter. However, when I did live home I never told them. I did go to great lengths to keep it hidden, I figured even if they did approve of it, they wouldn't want it in their face. I do have a feeling that my parent's probably had some suspicions but nothing was ever said.
So, personally my advice is don't mention it unless you really have to, and do a better job hiding your new/used stash.