Climbing and Life After 50

So recently my dad approached me and asked if I'd climb Denali with him. I've been eyeing this mountain ever since I moved up here and I imedately said yes without thinking. He turns 50 in January, not saying old people can't do anything, it's just kinda weird that he is asking me now. I still plan to climb with him but I set down some pretty strict workout guidelines, many different books he needs to read, and certifications that he needs to get. He agrees with it all and now wants to do Rainier as a warm up climb in March this year. Is he trying to make up for the lost time while he was raising me and my brother? Or does he see the end of the tracks and wants to do this before the train derails? I never will understand the inner workings of old people. Unless all they do is watch infomercials and eat pudding. I enjoy doing that as well sans the pudding.