Father Daughter rocky relationship

Okay so, will make this as short as possible. My parents have been unhappily married for 35+ years. My mom is literally my BEST FRIEND. There’s no one in this world that compares to her. She’s an avid Christian and has always been my number one fan. My dad on the other hand is an alcoholic. He was never abusive or mean, he was just absent. He financially supported our family but my mom filled the Dad void for me and my brother. He is currently in end stage liver failure due to his continued drinking even after being told he’s going to die. This may be a moot point because he may not even be here come March 2019, and if he is here, his mind is so messed up he’s clueless to what’s going on. BUT. If he is. He’s my Dad and I do have respect for him, so I will have him walk me down the aisle because without his financial support, my mom would have had to work more and wouldn’t have been by my side for 31 years. But what do I do for father/daughter dance?! I can’t find a song that works .. and also a gift?! It just feel so fake! anyone else have experience with this?