Thanks so much for your advice. I have IC for myself, and a family therapist for myself and the children. H has indicated that he'd like to be involved, and has talked to her alone, but we haven't yet had a session all together. As he blames me for the breakdown in the relationship between himself and eldest, my feeling is it would be better to stay out of it, let the two of them speak together with the therapist if they are both willing, and concentrate on taking suggestions from the therapist as to how I can support both kids and change anything that needs to change on my side that is negatively impacting their relationship with H. We'll see. R is not on the table between us - I can't consider that while he's treating one of my children this way - and he knows it, so it is time for me to be quiet and concentrate on myself.
