Does my ex have to be involved?
No, and they can't be. I only work with one parent, and I won't see the other one separately either, because you need to know this room is yours. If you and your ex both want to sit down with a third person to sort out arrangements, that's mediation, and I'll gladly point you to it. This is about you having somewhere to think, feel and plan that nobody else has a say in.