I'd take my mom to Vegas, eat like a pig and blow all our money on slots and cards.
... and then you'd end up like that guy on an episode of House who found out he was misdiagnosed or the cancer went surprisingly into remission. He'd already sold everything including his house to go on a wild vacation for the last of his days.
Oops!
I hear a lot of people, as they get older, say things like, "Make sure everyone knows that you love them." If they don't know by now, one day isn't going to be enough to make a difference in that for all but a few. Instead, I'd probably be extremely/carelessly bold and do things that could get me arrested and spend the last day in jail