Great to see you here, Jam!
We've only told a couple of people. I told my Mum (who told my Dad) just before my booking in appt, as I needed medical history information. And I've told a friend who already has a baby (coming up to 12 months) who kept badgering me about when I was going to join her 
I would love to tell a small group (parents, in-laws, siblings, siblings-in-law, close friends, etc.), but my MiL would be a bit of a problem. I love her to death and she's so great, but she can't keep a secret to save her life. I think it's because she's lonely (lost her husband, my FiL recently) and she uses news as a way to get attention.
Don't get me wrong, I don't mean this in a bad way. She's wonderful, and I really feel for her. We just know that as soon as she knows, the whole world would know (we'd get distant aunts and cousins phoning us to say congrats!).
And given we can't tell her, we feel bad about telling other close people, given how important she is to us.
So we're going to wait until the scan, which is when I'm 13 weeks (30th March).
I did tell my two managers on Monday this week, but that's only because my sickness has been getting quite bad, and I couldn't really hide it anymore (one of them said they had guessed anyway).