Help regarding speech

This is a tricky one. I'm due to get married next weekend and I'm currently writing my speech. My mother is giving me away because my parents got divorced when I was young and she reared me. However I've kept in touch with my dad over the years but we have a strange relationship. More like friends then father and daughter. Not much affection is shown and to be honest I really don't know him. He's coming to wedding but sitting with his brothers and sisters and wives etc I've asked him if he wanted to do a speech and he's said yeh. However I'm struggling with what I can put in my speech regarding a thank you etc towards him. I've so much to say about my sibling and my mother but when it comes to my dad all I have is "thanks for being here today to celebrate the day..." Anyone ever been in a similar situation and what did you say or how did you go about it? I appreciate any help or advice

My H2B is in a similar situation with his dad... his parents split up when he was younger and he hasnt had a great relationship with him since... He really didnt know what to say in the speech and I just said ... "What would you say if it was his funeral" I know it sounds very morbid but it actually made him think about it very differently and he thought of loads of nice things from his childhood and put a nice few lines together. Strange tip but it worked for him !!