My guess is that it isn't simply Daniel catching them have sex which got him all upset. He probably overheard them talking about Alex's intentions to get Lana pregnant again. This probably is just a set up to get Daniel so upset at Lana that he has less reservation when Sharon and Kiara make their move; we know Daniel has to confront them in order to get his money back. And then this "mother-son" trip is going to help mend their relationship. Alex will probably let them go on this trip (alone?) because he's standing witness to this "inexplicable" quarrel between Lana and Daniel. If Daval does take this route, I wouldn't mind as long as Kiara and Sharon don't get far with Daniel. In all honesty, I hope it's another "failure to seduce Daniel" moment like with Sofia, and Martha.