Tally, I fear if you start practicing avoidance it will become a habit, but a couple things:
Deaths often make people contemplate their lives and their worths. You or H may feel particularly close during this time , but you have to chalk it up to what it is. Can you do this, with H there? Remember,you are responsible for you. Not behaviour of H or mom etc. it's all you can control. If you feel H should be present, and he wants to go, by all means. Maybe explain to your mom that H was a huge part of this family for a long time. He will continue to be father of these children , your grandchildren, and continue to be a part of our lives regardless.