So sorry, tybec. As Forgotten said, there is no way of telling how these things will go. While you are there, talk to your mum. If she is considered non-responsive, she can still hear you. My Mom-mom (my mom's mother) was like that. I took an emergency flight home when my mom called to tell me the time was near and that the nurses had said if anyone wanted to see her they needed to come right away. We got to her room at about 11 pm and I held her hand, talked to her, and prayed. I was so worried I was hurting her because they said her skin was sensitive; she moaned a lot, even though I was trying to be careful, I wanted her to feel that I was there as well. I reminded her that all her children and grandchildren were grown up and doing okay. That we loved her. We left there and she died at about 2 in the morning. It's never easy.
The first husband was a jerk through tough family times. It had nothing to do with ex's or custody, just his abusive nature. It's hard, trying to balance family life and be compassionate about what your NG is feeling as well. For the holidays, make it great for your kids. If he gets himself together, good. If he ends up distant and only with his family, that's his issue.
{{{hugs}}} know that we are here. Sending positive thoughts all round!