CONGRATULATIONS, THAT IS AMAZING NEWS!!! I say tell him as soon as he gets home. I know I would not be able to wait.
As for the not telling, we waited till 3 months, but we had 3 friends who had miscarriages in the last year and I just did not want to have to explain it to every person who found out. My one friend lost her baby and she kept getting asked how the baby was and when she was due, etc.. and she had a bit of a break down one day. So, I just wanted to save myself from all of that. I told my mom and sister and MIL and that was it. Those are the people we would talk to if something happened, so we left it at that. I am happy we did it that way and I would do it again the next time around. But its totally a personal thing, I did want to tell the whole world because I was so excited, so I can see both sides. Whatever you decide will be the right decision for you and that is all that matters.