Interesting question...
It'd be ideal to follow the approach of Kantiansm(Do what benefits the most people) however, my own powers of persuasion would most likely lead me to this justification for saving my own child...
"Although I do not know what kind of man my child would become, atleast I have some control over making him a moral and ethical person. The individuals on the other side of fate's pendulum have no connection to me, I can not be sure that any of them are good people and me and my family's life are more important to MY universe of thoughts, thus my son's life is more valuable."
So I'd ultimately I'd be on a barren planet w/ me & my son, contemplating my decision for the rest of my days. It be a catch 22 either way.