Telling 8.5 yo so about baby

Tia

So I have an 8.5 year old son from my prior marriage. He’s obviously used to being the only and does not deal well with change, even the smallest things like getting new furniture, moving his bedroom around, getting a dog (who he now loves). But with this, he will be the first person we tell, but how can we try to make it so exciting for him? Maybe during an activity? I just know he will feel like he will be ignored, which was his worry when we got a dog. He’s so sweet but I want to try and make him excited about it. Thank you for any ideas!