My father-in-law was estranged from one of his daughters and decided to leave her “share” to her children.
He died a few years ago and the grandchildren on that side of the family had the money put in trust till they were 18.
That seemed to be a good solution and pleased my mother-in-law (second marriage so not her children) as it felt “fair”.
Maybe you could consider something similar?
I'm Sure It's a Repeat of the Summer of 1976


