I don't really know your life, but in my experience cutting people out wholesale is a mistake. The reason being that you might need them someday, and only the forgiving ones will take you back.
On the other hand, if you're wanting a radical change, then I've found that telling everyone is a big mistake... because people will naturally want to relate to you as the same old person, as part of their comfort zone. They might try to hold you in place.
So... it's best to figure out which people might be the most supportive of your desire to break free, and tell them. They can inform the others who don't know, if it comes up. You'll want the most understanding people as allies anyway. The others will just question you and make you doubt yourself.
But saying nothing to everyone? Kind of crummy for them.