[@tsukune]

I think that the third one sounds best, maybe Aphrodite could have something against one of our characters' grandparents (Gods) so she's putting out her frustration and anger on them. Maybe the first idea actually, :hmm. Aphrodite could always of asked Dionysus at Camp Half-Blood to send two certain demigods (that she has a grudge against) to get her the Necklace of Harmonia so he gives these two demigods (our characters) the quest thinking that they will never survive.

Maybe we could even mix all three, they could bump into each other and crash into Rachel's cabin, while the Oracle is telling them the prophecy Aphrodite could convince (which wouldn't be too hard) Dionysus to send these demigods on the quest for the Necklace of Harmonia. He could get Chiron to do it, not telling Chiron his intentions which is to kill the demigods off as he hates having to be at Camp Half-Blood and not being able to drink wine. All three into one.