As the father of two very successful young adults, my advice is that I think you can simply give your father a nicely hand-written note that says:
"Dad, you are reason I got into aviation. Thanks for the motivation and advice through my first 20 hours."
You can expand on that to more closely reflect your joy in flying, your respect for your father's own achievements and the value you place on his example, sacrifices and probably some toleration of your own foibles while growing up.
I know I appreciate hearing that the values I tried to pass along to my children are important to them in their lives today. Fortunately, I can buy my own ties, liquor, and shaving accessories. What I treasure is the sense that, in spite of my many short comings as a father, they got "it" and "it" helps them in their adult lives.
And don't watch if he tears up. That is bad manners.
Scott