Social media announcement

Ok, so I’m weeks away from announcing to the public on social media... but I can’t sleep and I can’t help but plan the announcement in my head. I’ve seen wedding invitations where it’s a picture of the bride and groom from their childhood and it says “these kids are getting married.” I was thinking of doing something similar to announce my pregnancy but I’m not sure how to go about it. I was thinking a baby picture me and the father like, my picture + his picture = the ultrasound picture. Will people get it? And I’ve never edited photos before, what’s a good app to use for putting this together if we go this route?