Pressured to announce

Mallory • I`m 27 and expecting my first after 7 months of TTC with endometriosis, PCOS and hypothyroidism.
I'm really concerned about miscarriage but all in all everything has been routine and I've had a normal ultrasound at 7w3d and heard the heartbeat strong at 144bpm. My husband is desperate to tell my stepson, his son from a previous relationship about the pregnancy. We have discussed that because of the tumultuous relationship with stepsons mom that we will tell stepson on one of our weekends with him so he can process his feelings in a safe environment without negative opinions being expressed to him. Overall we know stepson will be excited. He's 7 and begs for a little brother or sister all the time. My husband basically told me that we will tell my stepson this weekend when I am 9 weeks whether I want to or not. The predicament is we can definitely do that but I feel like at that point I have to announce to everyone or else allow his ex to tell the whole town in such a negative way. This is such an exciting time for us and I want to be able to experience all the wonderful fun of sharing our news myself. Thoughts? Would you tell stepson and still wait a few weeks to share publicly or just tell everyone since the ex probably will anyway and at least then I have control over how the news is shared? This baby is such a blessing and I don't want anyone thinking otherwise.