aggh, that sux big time!! i hope you are able to make the anoucment yourselves in 2 weeks, and those who do know still react as they should, with love support and excitement, not with "oh i already knew"
my cousion done that a few months ago to my aunt, put a huge congrats on fb as she over heard the convo with her mum, my aunt only just found out herself! had calls left right and center, so had to announce it to the world at 5 weeks.