I'm very sorry for your diagnosis and shortened time.
I've a friend living in FL, a long distance from me, who has a fabulous old vinyl collection. A few years ago she said she is going to tash all of them because of lack of storage space. I was appalled - no, horrified. She spent 10mins just naming most all of her old great top 40 hits I love. She told me mailing them to me would cost too much, so I told her I'd pay the ~$100 in shipping cost. She dropped the subject but because of your post, I'll ask her about them again.
You know, folks just don't seem to value things as they used to. Just like the friend I mention above. They "move on" so very quickly. I'm a very nostalgic person, sometimes unfortunately so.
My hubby tries to "comfort" me by the fact that none of us will be living in less than 100 yrs, So I need to stop valuing THINGS so much. The planet will mostly be dead in a 100 yrs.
Over the last couple of years I cried for months trying to reconcile myself to this fact. Because I have a child, it is deeply, deeply disturbing and sad to me, even more so than even my own mortality. (I'm an atheist, not believing in an afterlife.)
Because of my age, I'm adjusting and trying to refine my process of "letting go" - of things and my life.
Sorry I cannot offer any better advice except to say that IF you put a BIG price on your collection, would the buyer not value it? Get to know that person, the buyer, and share your concerns and your love of these records.
Good luck!