You don't need to 'stay strong' in front of your Dad, it's ok to share all your emotions - to laugh and cry together, to tell him that you're scared, sad, bereft, unsure how to act or how to help . . .everything. Let him be a comfort to you from time to time, so he's still acting the role of father rather than patient.

Help when and where you can. Be his advocate/companion, when he sees his doctors. Ask him how he feels about dying, don't hide away from it. Help him with arrangements. Sit with him in companionable silence. 

Please note te above is all just my personal opinion. All, some or none of it might be relevant to you you and whatever you do, you will not be wrong. I'm a Dad of 6 adult children with a wife and I'm the one with cancer and a recent colostomy.

We've done all the emotional sharing, talked about dying and funerals, laughed, cried, screamed at each other and cried and laughed some more.

And now my children are getting on with their lives, which is important to me. But they will drop everything and rally round when the need arises.

So I say concentrate on today and today's quality of life.

Regards

Taff