We had not told anyone when we lost our first at 7weeks.

For DS we waited to tell our families until after the 12 week scan to make sure all was ok. I told work at 24 weeks as I was still not really showing then.

Since we lived remotely, and I did not really want to announce on facebook, most of our friends in the real world did not find out until I moved to syd temporarily 6 weeks before ds was due. They pretty much figured it out when we were having catch ups

Its so personal and I would go with what feels right for you. At the end of the day if the people you want to know are in the loop, the others can wait until your 6 year old bursts with excitement!