I personally would call, but if you want to ALSO post a “flyer” at Shul, I did the following:
With grateful hearts filled with much joy
We’re blessed with a new baby boy.
To celebrate our great delight
Please join with us on Friday night
As we welcome our new little bochur
At the _____ Mishpacha’s Sholom Zochor.
(give address and time)
My wording was a little different, but you get the idea…
mazel tov and much nachas as you are zocheh l’gadlo l’Torah, l’chuppah, ul’maasim tovim.