I'm 5-yrs into RCC and have a long saga of operations and radiation treatments and chemo therapy. I'm 60 yrs old and understand your father's need to protect his family from a continuous stream of bad news that often goes with this disease. I have two children in their twenties and have found it distressing telling them the latest bit of news as it has usually been bad. However, by being more open with my friends and family I have grown closer and been able to express my love for them even more. The last 12-months has been very hard for me but I have enjoyed my time with my family more than ever.
My advice is to try ways to get your father to open up more to you and understand that you love him and want to be with him through the bad times as well as the good ones.
Keep finding ways of making the most of your time together.
Keith