I hear what you're saying Charlyfrog
I told close family at about 8 weeks, but my Dad found it soooo hard to keep to himself. My DH was getting really angry with him, because at a family bbq he was talking really loudly to us about it, just so someone would hear. We waited until 12 weeks for our second, but it was sooo hard not to tell my mum. If we are lucky enough to have to announce our third, i think will tell everyone early, because as you said, if something does go wrong, you will have the support there.