i like trill's advice...
personally i wouldnt tell our families but that'smore our situation and the way i am. if you think it will be valuable to you to have their support etc then i would tell them... but set some guidelines as to how much involvement you want themt o have (ie asking qs) and how much you want to talk about it... and if you want them to not say anything to anyone make sure they know it!
good luck - i hope you get that BFP soon.