fancy, only you know. But I had a google for opinions, and one person said that they didn't tell anyone, then had a mc. They needed support from their friends, so told them about the mc. The friends were obviously supportive, but sad that they missed out in the happiness of the news and only got to share the sad bit. Next time they told them earlier.
I figure that if I want/need the support from someone if I did mc, then I'd tell that person. If it's close family who will be over the moon for you, but support you in whichever way you need (and that might be just leaving you alone), then I'd tell them and enjoy sharing the happy news.
That's just me though, I am by nature an over sharer, as is DH. The only way anyone close to us will not know before 12 weeks is if we manage to avoid seeing them!