Dee, I'm going to speak from the heart. I don't think you need to get involved, at all. This is something between Larry and his children. It may not be that the children are so much selfish as they are harboring deep rooted emotions from the past. Only the children and your husband can uncover and heal those feelings, whatever they are, or stem from. The healing should be between them and Larry. The best thing you can do is be available to not be available when the time comes, if it ever does. Larry may have to deal with LW and D, one at a time, separately and in different manners. There is some underlying problem that needs to surface, make itself known. Larry may not be able to see it on his own, but he is the DAD... maybe you can help him in that way... trying to discover the missing link.
Hope I haven't offended, but I'm living the child's side of a similar situation, and I'm contributing my thoughts from that angle.