This is something that you should post in discussions because presumably you want a lot of different answers.
For me, there is no question but that I would spend the day with my wife and kids. It would be pretty sad, of course, but there is nothing else that I would rather do. If I were going to die in 24 hours, I would want those last 24 hours to be spent with the people that I care the most about. As far as what I would do with them, I think (they're 9 and 6) that we would play games, maybe go for a hike, things like that. It would allow us to spend time together having fun in ways that hopefully they would later remember.