I think the honorable thing for Buffet to do would be to set up some kind of annuities for his kids and grandkids so that they will be taken care of for life. After that, He should help American charities that are actually helping people, and after that, I don't mind if he helps people in other countries.
I think it was wise of him to not let his grandkids live like rich kids growing up. I don't think it's wise not to take care of his own family even if she did something to anger him.