Announcing a rainbow baby.

I start vacation from work soon but I think I want to announce my rainbow baby on Facebook before I go back. I'll be around 6 weeks at the end of vacation. I don't want to do a full blown Facebook announcement tho just want to let me friends at work know before I get back so they won't work me like a mule lol Any idea how the privacy filters on Facebook are? Like if I only post to a group of people will anyone outside of that group be able to see it? ❤️✌🏼🤞🏼