I imagine by not telling your family about your current arrangement, even though things have gone well for you, you might have a sort of incomplete feeling about your life. It would be sort of like going on a great vacation and then not being able to tell anyone about it or show them the photos. Not only that, you'd always have the feeling that any day someone from your family might arrive up at the doorstep or that somehow the whole matter had been discovered and you'd then be forced to deal with the topic on their time table.
I like the idea of breaking it to them gently over a period of time. Little indications that you've met someone without rubbing their noses in it. They must realize on some level that you have not been living like a Monk. Either way, all of us who have left the organization have had to make a similar choice. Do we just play along with the game and smolder inside or do we get it over with and suffer the consequences what ever they may be. This is the hard reality for those of us who one way or another, wound up being part of a religious cult.