Father of the bride can no longer travel to wedding, what do we do?

Sorry this is a long post but I could use some advice. I’ve found myself in what seems like an impossible situation at the moment and I’m not sure what the right thing to do is. I’m from the US and my fiancé is from the U.K. Our wedding is taking place May 2021 and we’ve planned quite a bit for it already. It’s planned for the U.K. as he has a lot of friends and family here he wants at the wedding and my mother and grandfather now also live in the U.K. A few days ago, I found out my dad, who still lives in the US, is unlikely to be able to fly over because of illness. It’s breaking my heart thinking of not have my father there on my wedding day, especially as I get to see him so infrequently, and I’m his only child. I would be happy to cancel everything, buy all the immediate family flights and have a small wedding in my hometown, however, my fiancé’s mother also has a health condition and cannot ever fly again. Which means we have to have a wedding without one of our parents there. My fiancé wants to carry on with the wedding here without my dad and I wouldn't feel right planning something without his mum, but it seems unfair when my dad already misses so much and the father of the bride is such a key role on the day and since his mum has already gotten to go to one of her four children’s weddings. I’m tempted to plan a second, small ceremony in my hometown for my dad but not sure it would feel as special given the real ceremony would take place in the U.K. and he’d still feel left out, and we aren't sure we can afford it. Of course none of this might matter at all if the pandemic situation is still bad next year!