announcement help!

I'm due sept 18th and was thinking about announcing on Facebook for all distant relatives and friends on st. Party's day! We got a onesie today that says 'mommys lucky charm' and was thinking about posting a picture and having a cute saying as a caption! Taking a pic of just the onsie looks kinda weird but idk what else to put in the pic, we don't have an ultrasound pic yet. Any ideas on what to say as the caption and how to take the picture??