That is the question. I have the feeling that this game could be of a higher quality than the mindless incest harem games where everybody just swoons when they see the Mighty Dick of the MC regardless of how they are related to him.
If there is a dilemma presented to the player about what he wants the outcome to be, then there are also reasons not to choose the corrupting options, like peeking, feeling her up, sleep sex etc. On the other hand, a mechanic like "corrution +1, love -1" could also work in these cases, where corruption > 10 => corruption path and love > 10 => love path.
Anyway, a game aiming for realism without such meaningful choices would be meaningless.
To be fully clear, I am not talking about the MC getting off on it, or the sex between Kailey and the third person being shown or even implied to on screen. That is not at all what I am suggesting. If there were to be such an ending, I hope she stays a virgin until marriage and the person she ends up with to be a genuinely good and likeable person.
Again, that would be the best solution any father could hope for IRL.