Hi Fullsteam, Its hard to know when to accommodate your kids wishes and when to make your STBXH handle their emotions. My thought is that he wanted you there because he didn't want to have to deal with their sadness. If you are not there, he has to deal with it and take responsibility for it. The one who makes the decision to end the marriage often doesn't want to "feel" the pain that he/she has caused the kids or the XS. If you are there to buffer it, then probably you are doing what you've always done in the marriage...
Its hard being in your situation when the kids confide in you but protect their dad from their real feelings. And its hard to know when to accommodate their wishes. I've kind of drawn the line at holidays--their birthdays, Christmas, Halloween. I do accommodate family time on those days, for the kids, but its hard on me. I don't know if its the right thing to do or not...