steph,
i expect that your daughter already knows that you are lovely, so i wouldn't freak out too much, she likely will take it well, just let the announcement find its natural time; i have told all the people i had to, including some i only know slightly, because it was necessary, but only about 1/2 my friends, because the time hasn't come, but it will soon, and i am looking forward to it.
so good luck with that, you have a strong family, and of course you know best what to do, and when.
xxx ooo