Assuming that it happens on a weekday, the first thing I will do is to leave office immediately, and send an email to my boss later. Then, I will call my wife to take emergency leave and then pick her up and go home.
The rest of things that I will do include:
Use my camcorder to record words that I wanna tell my son when he grows up. Most likely will be by topics, like a section about attitude to learn, another about dealing with girl/woman and on marriage, etc. Then, I guess I will record my will as well, so that all monetary issues are settled.
I will order all the foods that I wanna eat, like crabs, sushi, pizza, ribs, all sorts of fruits, desserts, etc.
I will pass the passwords and accounts of all my stuff to my love ones.
I will call my immediate family to be with me and my wife + my son, then spend the rest of the day with them.
I may listen to few songs that I like.
Of course, I need to comfort my family and love ones emotionally to make sure they are ok after my departure. I don’t want to see them cry.
By the time that all these are done, I think there is not much time left. I guess I will just say “I love you and Goodbye” to all of them. Then, close my eyes with a smile.