(Jessica) My father and boundries

My father made a commitment he did not fulfill. He stated he would come to my area for a visit (he lives out of state) and pick up my developmentally delayed brother on the way to my house so we could all visit together for my brothers birthday. I agreed since I was caring for my ill mother and did not have time to pick my brother up for his birthday visit. As a side note, I am the guardian for my brother because my father did not want to have to make choices for him and my mother is too ill to make informed choices for him.
My dad informed my mother (they have a co-dependent relationship long after their divorce) he will not be able to come to town due to other obligations. Insert my furry and anger that I am trying to do thought downloads and models on.
I cannot allow him to do this to me, my family or my bother any more. He has made statements like this in the past about coming home and followed through a couple of times recently but in the past never followed through. I feel duped again and extremely sad for my brother who is mentally the age of an 8 year old in a 38 year old body who is looking forward to seeing his father and extremely disappointed. I realize I need to set some boundaries for me and my brother. I know I cannot make him do anything and he will never follow my rule book.
So, my thoughts are to tell him he has the right to come for a visit when ever he wants but without any fore thought or planning me, my daughter and brother will not be able to commit to seeing him. He will only get to see my brother if I have dates ahead of time and my brother will never be told of his visit. It will be a surprise for him if he does get to see his dad. My father is welcome to call him but will not be allowed to discuss a visit and if I hear he is discussing visits his privilege to talk with him will be taken away.
While we love him and would love for him to be part of our lives it is my responsibility to decrease as much emotional damage as possible for my brother. Thoughts?