I'm so sorry, OP.
I was hoping this was just hypothetical. And I'm glad that it still is, in a way.
But I do still think that the main thing is time. Just make sure you spend the best, quality time with your kids that you can.
My parents used to do a monthly 'thing' with each of us. Such as, in January, Dad did something with me, and Mum did something with my brother, then the next month Mum did something with me etc.
The 'things' were simple, I remember Dad taking me to the movies and Mum taking me to a ballet. Dad took my brother to an airshow. Things like that. But we both still remember those experiences - vividly! Even though we were only really young. I don't remember most of the stuff they bought me, I remember the things we did. I remember Dad making me a balance beam in the backyard and helping me practicing balancing because the PE teacher said I was a bit of a klutz. I remember Mum taking me out of school early because it was such a hot day that she thought I'd like to go swimming
These are the things that kids remember, these are the things that made my childhood a happy one.
Gosh, this has all inspired me now! Thanks, OP. I'm going to spend the Christmas break thinking of ways I can intentionally 'hang out' with my kids and give them experiences to remember. The reality is, health problems or no health problems, none of us know how much longer we have.