The way I look at this situation goes like this... when a convict is sentenced for execution, they allow him/her to have one-last of their choice before death, as part of their dying wish.

And I think the same principle applies here, your dad is dying and the only thing he wishes for before he departs this world is to see his grandchild. In a situation like this I think the best solution is to temporarily forget about the past and just do it... because your did literally won’t live to regret not doing what he did to you because he didn’t get to see his granddaughter... that’s not to say that he doesn’t already regret it, as am sure both of your parents do.

Your are definitely not obligated to forgive, but just set all of that aside for a second and give a man his dying wish.