WAH, in the thick of divorce (pt 3)

[ep0215]

I need help setting a boundary and being stern. H texted me this morning to say that his mother was going to pick up S4 from school early because he had a meeting after work so he wouldn't be done until late. Wednesday are my night form 5-7 unless I can't watch him. I texted him back saying that was fine as long as she dropped him off at the church event we were already going to. He wrote back that I should call her and work it out.

I just got a long text from his Mom when I texted her if she had a minute to talk logistics for tonight.

Mom: "I had told S that I would be picking him up early and he was excited. We are decorating for Halloween and I made dinner. If I had known about church I wouldn't have promised, now he will think I forgot. I need to know his schedule so I don't promise something I cannot keep"

Me: The same can be said for me, I was unaware that the normal schedule had changed until this morning. I didn't know you had made plans.

So I want to text H and say:
The schedule is for me to have S4 on Wed from 5-7 unless I can't watch him.I don't mind if your Mom or anyone wants to do things with him but if it takes place on my time then I need it to be cleared through me first.

What do you think? Too harsh. I am so sick of this BS happening every other week. I need to set my foot down.