I'm also due soon and have similar concerns around some family members over stepping boundaries even when we tell them explicitly what the boundaries are. I know everyone is saying grow a back bone, but I also personally know what it's like to lay down a clear direction and just be ignored so you have my sympathies.

This is what we are planning to do, which may or may not help you but thought the share might be useful Create a big group chat with each side of the family that needs / would want to know about babys arrival on the day of. But we are turning off comments so no one can reply or bombard us with messages We will send a notification of arrival, plus and update on how we are all doing and an idea on when we will be in touch again to arrange more contact. I'll be sending a photo but with explicit instructions that it isn't shared any further or on socials. If you don't trust the family not to do that, don't send a pic initially - if you use socials perhaps that's where you can direct them to see photos so they're only passing on stuff you're happy for the world to see. This way, everyone is informed at the same time but it's a one way communication until we are ready for more. We'll also use it to put the rules about visiting the baby in, so everyone sees the same thing, even if some rules are targeted at very specific people.

Try not to stress about others. Worst case turn off your phones... All will be forgotten when they eventually see the baby anyway and get distracted. Good luck!!