for certain issues and treatment, you aren't supposed to discuss certain things. There is no manual or educational material, it's only if you do or say something "wrong" will the expert or therapist then let you know.
I find this extremely troubling; once something is said, it can't be unsaid, so how is this approach even helpful??
If the therapist can't guide you beforehand, I would stick to topics that can be resolved by the family members present. Your feeling overwhelmed, while a definite problem, is not something that your kids can alleviate. Perhaps you could present it in terms of "If I do this, I don't have the time/energy/ability to do that" and let the kids brainstorm on what they find most helpful from you.
As far as feeling watched and tormented by your X and owife, those sound like legal issues. Perhaps you could get some legal counseling on how to deal with those idiots and not feel oppressed by them.
Good luck; I can't imagine how difficult this is for you. (((((wgb)))))