You're being a chicken.
Take a page from Bitchy Bella.
![Laughing](https://cdn2.able2know.org/images/v5/emoticons/icon_lol.gif)
Be straighforward, honest and keep it short. Make it clear that you don't have a problem with them seeing Mo, if that is what he decides he wants, but that it will have to be around your plans.
You will have to stand up for Mo for many years to come. You have to buck up. He'll be watching and learning how to stand up for himself, so make him proud.
You can do this! You've already gone through tougher things. What are they gonna do? It will be by phone. They aren't gonna hurt you.