Trusting, Well, although OW shouldn't have the say, I am inclined to think that the kids should understand that participation in the events honors their grandmother. I'm not sure if I would make an older child go. I might. But that's what your X should say, not OW.
Your X is under some extremely stressful conditions. His R is not good, he lost a family member, money worries, etc.. So of course he is very very stressed out.
I would not look at this as having anything to do with you. It's not. It is that H has to have OW play a certain role here that is generally reserved for family members, and his R is not good. Also, the stress of losing a family member takes a very long time.
I would expect an explosion from him, just because of where he is right now. At least I would expect it from my H. Just don't assume it's about you. If possible, it might be worth it to say gently "This isn't about me, and I am sorry about all the things that have been happening."
I do hope you had an after-hours goodbye.
M: 16 years Bomb 4/07 OW 20s long gone Divorced 11/09 I remarried New Guy Cooperative r w/X regarding D