Lana have more to lose, since it's not only infidelity, it's morally wrong and illegal, Sofia will be a cheater fucking someone half her age, Lana will be a cheater fucking her own son...
But I agree with something! Daniel is smart, even if Sofia find out about it and try to blackmail them, he will find a way to revert the situation, if it were up to Lana, she would give in to Sofia's demands without much resistance.
Well by a good guess, it's just not. Sofia does have more to lose, not only because of the multiple infidelities to her husband [Sofia mentions in chapter 5 that she cheated on her husband more than several times with that guy, something she told Lana] But also because of trying to cheat on her husband again with Daniel, trying to fuck her [friend's] son, sucking her friend's son's penis. Which brings us to the other point: buying lingerie with her friend's son. Posing her naked tits in front of him [That happens in chapter 6] Also, of course, letting Daniel touch her pussy and tits by the pool, things that Martha and Lana saw. Also, Sofia masturbated while Lana and Daniel were fucking thinking she was with Alex, which is at the very least a morally questionable act.
It depends, in some states in the US incest is not illegal, I think since we don't know where they are actually located that doesn't apply. Well, I don't think Sofia fits the morally correct person category, you know. Besides, come on, we're talking about Daniel, the game works his way, not Lana's or Sofia's, it's Daniel's game and he decides how it goes. Much less if his relationship with Lana is in danger. After all, Daniel has shown that he has no limits or scruples when it comes to Lana, but we'll see what Daval chooses.