If you want to tell everyone in your family or a particular group something you can tell one person and they spread the news like wildfire. It's what they do. I have several in my family and this type of person is exactly why the fact I mystery shop is a closely held secret.
Unfortunately for you the cat is out of the bag with your family member. You might have to resort to extreme measures like getting another dinner companion/driver and lying about your work. Tell them you quit, or reinvent your business for them as something like consulting, auditing, merchandising or the like.
Good luck.
Happily shopping Rhode Island and nearby Massachusetts and Connecticut