I refused to pray for my dad when he was having a heart attack
Do you think he will be saved by the doctors?
Maybe he will be, maybe not.
Parents can do many things that upset you, but you should still care about them if they get sick. Otherwise people will think you are heartless.
I'm still not going to pray that he gets rescued, I will never forgive him for not taking me to an amusement park just because he didn't feel like it.
However much your father's refusal to take you to an amusement park still upsets you to this day, you should at least put things in perspective.  Your father might not survive, so this could very well be your last chance to forgive him.  At least let your family know that you are praying for him now, and if he recovers, you can talk about the amusement park together.