There is no doubling. The animation already exists. Larian just needs to swap two models.
If that's the case, I would hope everybody has the option every time, but as Niara points out above, with what we've seen so far, that's appears unlikely.
And if that's the case, I'm going to be a little angry, because for all the "the game is about choice" over and over, if choices about how we screw aren't present, why would they include these scenes at all?
