Telling 2 1/2 yo they are going to be a big brother

When did you tell your child they were going to have a sibling? We are planning on sharing with family after my 1st ultrasound around 12 weeks. But we also happen to moving cross country at that same time (moving that weekend, 1st apt Monday morning 🤯) I’m a little worried about overwhelming him (I mean... I’m overwhelmed 😬 & I’m an adult lol), but it also seems weird to be telling others when he doesn’t know yet. When did you tell your kids? How did it go? Should I wait or tell him before we start telling others?