My husband and I announced to the public at 8 weeks. To close friends and family was 6 weeks. It's really up to you. Although I know a lot of people wait til 12 weeks just to make sure everything is ok.
I didn't tell my parents until almost 4 months and when they finally got me to a doctor I had to get all the exams, tests, etc done ASAP to catch up what I missed the first months ..but kind of exciting because I didn't have to wait
I think it's best too right away so you can have help and support
I waited untill after the 1st trimester just to make sure everything was fine.