I like what you imagine for Luna, Draco, and the children they have with their respective spouses. I can't see Scorpius turning out the same as his father during Hogwarts. I can't see Rose turning her nose up at the idea of befriending him. Ron and Hermione raised their children better than that.
For some reason, I just can't see Luna setting down and starting a family in one single place permanently. I don't think she would sleep around, but I think she would rather be more 'free' to do what she wishes–not necessarily with other people.
I am curious to see what you think of the other four's lives after Hogwarts.
