I usually just causally drop it in conversation with family, like "Gee, my pants are getting too tight, you want to go maternity clothes shopping with me?" or, "I'd love to have the spaghetti, but this morning sickness is a killer."
I love how everyone just stares all confused and they are like, "what?, "are you serious?", "repeat that again?"... then I can't hold the laughter/smiles back and everyone just has the biggest laugh. I don't know, maybe I'm just weird! Not very memorable, or big announcement wise, but fun for me.
You can have your little girl tell them in a cute way. Maybe get her a new baby doll and take it from there. Show up to their house with a bundle of "congrats" and "baby" balloons.