I was executor of my father's will because my brother, the joint executor didn't want to be bothered, and signed for me to be sole executor. It involved me doing multiple trips of several hundred miles and the physical task of clearing the house which took ages, sorting out all finances, arranging the funeral, selling the house etc. Eventually I was fed up of bearing the time and money costs alone and claimed my petrol and one hotel overnight stay. I don't feel that was unreasonable and in fact my brother said he hoped I'd taken petrol money. My father's will left it equally to us but if one of us had died, everything went to the surviving child. That's what he wanted, it was his money, why shouldn't he dictate its distribution? In our case it didn't come into play.
I do find it strange that so many people think grandchildren who didn't bother with a grandparent should expect to inherit. It's almost as if the elderly have no right over their finances. Jannabell your father decided what he wanted done with his legacy, you influenced him to be more generous to the grandchildren. Distribute it, then forget grasping relatives.