The daughter has spent what sounds like decades to me in pain, she decided to share that with her father and he closed her down.
At the moment when she was looking to get past what is hurting her, he refused and walked away.
This could have irreparably damaged their relationship for good.
The father should go to her house, ask her to read the letter again, listen and acknowledge her pain. Tell he loves her, didn't mean to hurt her and help her to come to terms with the past. If he wants to see her and his grandchildren again he will need to be the bigger person and make amends.
If she refuses despite his efforts to see her, he should write to her and tell her he is for her, that he loves and will listen when she is ready.
He should continue to send presents, cards and things to his grandchildren in the meantime.
Respecting her choice not to see him, but telling her he is there in an indirect non confrontational way is all he can do now.
Nothing to do with other members I would recommend they stay out of it, it is between them.
He should have listened to her when he had the chance....this situation was a long time coming is my guess.