Family member passing close to wedding date

So, my mother’s husband and I are not what you’d call close. Basically I tolerate him for the sake of my mom. We don’t see them often as they live a couple hours away.
Anyway, the point is, he was diagnosed with an aggressive lung cancer that has mestastacized (or however you spell it) to his brain. He was given “4 week to 4 months” to live when he was discharged from the hospital. He’s home now with hospice care.
My wedding is in 4 1/2 months. I’m concerned that he may pass right before the wedding or be alive but in terrible condition. How do I handle this? My mom & him have had their problems but on some level she will be sad and miss him or worry about him. How do I make it ok for her to enjoy my wedding?