If Darth Vader were my father!
If I were Luke Skywalker, I would have been taken Darth Vader's hand when he found out that Vader was his father. Seriously, ruling the Galaxy! Dang! That's better than what the Devil offers!
Really, if I were Luke, I would have said yes to Darth Vader at Cloud City. I would have learned the art of the dark side and taken total control. I'd play the game for a bit and then make my move.
Yes, both the Emperor and Darth Vader would have gone down together. They would understand since it would be the evil thing to do, right? I mean, that's how they got powerful themselves, by betraying their friends, right? Darth Vader would surely understand!
I would still be mad about the hand though. You know! Also have to consider which hand too! Vader could be more considerate before chopping hands off!
Anyway, this father thing goes on with Han Solo and Kylo Ren in the new trilogy. Han offers his hand to bring Kylo out of the dark, but Kylo decides to kill Han. Kylo decides to kill Han to get rid of his past, but fans believe that Kylo sacrifice Han, his father, to get close to Snoke.
It is theorized that Kylo wants to get close to Snoke to kill him and get rid of the new evil leader that is threatening the galaxy. That is why Kylo is also seen talking to Vaders burnt helmet stating that he sill finish what his grandfather, Vader, started.
Anyway, if I were Luke, I would have accepted the hand and taken down Vader and the Palpatine. After that, I would have turn to the light and made the Galaxy a better place to live. However, that would not have been a good story line, and it would have affected the story line for Return of the Jedi.