My only question would have been how close were the kids to this GGF? While I understand paying respects and supporting family, if there was not a connection, and the don't want to attend, let it go.
I don't think OW is making your H do anything, and never has, he's an adult who has made and is making choices.
I'm so sorry, you sound miserable.
Me 57/H 58 M36 S 2.5yrs R 12/13
Let me give up the need to know why things happen as they do. I will never know and constant wondering is constant suffering. Caroline Myss