My Father dying distancing himself
You are in a very sad and upsetting position. When a parent has a terminal illness it is so hard, and you want to do what you can in the time remaining, to show love and help them leave legacy of good memories behind -as well as help them make the most of the remaining time.
I've been in the situation your father is, but it turned out to be a false alarm, however it does give me a little insight. The first thing of course is that being told about such a condition does not grant wisdom, or acceptance or much of anything. The person concerned has no road-map to follow, no guidelines at all. Just finding out how one feels about it can take an awful lot of time.
In the meantime by far the easiest way to go is 'business as usual' particularly if symptoms are not too intrusive. Having others - no matter how loved - try to fix or organize, even when done in love and with sympathy, can be unwelcome.
At this stage I guess the kindest thing you can do for your dad is follow his lead. If he says 'all good' and changes the subject then go with it. All you really need to do is keep an eye out to see if his thoughts and behavior changes, and react to the new circumstances if and when they happen.
It would not surprise me in the least if later on his attitude does change. The one good thing is I'm sure he would feel loved.
You know you can talk here as often as you'd like
It is a very difficult and emotional position for you and your dad.
Croix has given helpful advice so I won't repeat what he said.
Sometimes your dad maybe be reassuring you that everything is ok as he does not want to worry you as you are coping with your child. Maybe he does not want to worry you.
I wrote a letter to my dad once even though we were close, we used to argue and I wanted him to know how much I loved him. I was so glad I did. I am not sure if that would be appropriate for you but is just an idea.
I guess you have to ask yourself if the time is in fact being wasted. If your dad knows you are deliberately following his lead to make things easier for him, then I don't think it is wasted at all.
Quirky has mentioned two pretty good points, firstly that parents under these circumstances may indeed wish to shield there children, and secondly a letter might be an excellent idea.