Like a lot of others, I'd spend that time with my family and pets. Doesn't even have to be anything grandiose, just being together would suffice. Also sell just about everything I own and use the money for a few things:
-buy a saxophone. I've wanted to learn to play the sax for years, but for one reason or another my broke, lazy ass still hasn't gotten around to getting one.
-Go to as many nearby animal shelters as possible and get as many cats and dogs, mainly any old, inured ones that normally have a hard time finding a home. I have family that live out in the countryside with lots of land, and they let me stay there as long as I help out around the house with chores/upkeep, so I'd let the animals live in peace in a loving home before everything ends.
-If there's enough money left over from the above (including after cat/dog food expenses), I'd buy a guitar, another thing I've wanted to do for years now.
My final days would be spent enjoying my favorite meals and time with my family and pets, playing the saxophone/guitar. Might also get some ayahuasca/shrooms to take when earth's final moments come.