Who should walk me down the aisle?

My biological father and my mum split when I was 1. I saw him every week until I was a teen then saw him as & when. After I’d been living with my fiancé for a while, he just stopped contact! For no apparent reason. We got back in touch last year but with no explanation for his strange behaviour. He’s been over for dinners, for evenings with me and my fiancé, he’s taken the kids out etc. But now he’s distanced himself again. He’s renowned for having a “screw loose” but I’m scared he’d be a no show :( My father in law is wonderful. Since we moved in together in 2011, he visited every other Sunday night, up until June last year. Since then he has been to see us twice: once to drop off a birthday gift for one of the kids and once to see the new baby. No explanation, he still works with my fiancé, they still chat on the phone etc but it just stopped. (My fiancé thinks it’s his sisters doing, as FIL visited us regularly for years but not her, so perhaps she had enough & said something). I know he’d drop everything in a heartbeat to help us out if we ever needed him, but it’s still strange... Then I have my uncle. Married to my aunt since before I was born. However he has 3 daughters of his own and I don’t really want to be the first person he walks down the aisle, especially as my father and my father in law both have legs!! The wedding is in 6 months. For so long, I’ve been certain I’d just do the walk alone. But the more I think about it, the more it terrifies me!! Shall I pick my dad solely because he’s my dad? (Im his only child and would feel horribly guilty if I denied him that chance. I know it’s ultimately my day but I don’t know if I’d forgive myself). I could have my father in law as backup? Or pick my uncle because he’s the safest option? I’m really torn. Did anyone else walk it alone? If so how was it?