This started to make a little more sense last night when it was suggested that there may have been adult drugs in the Apt. Not that they gave the kid the drugs, but that the kid may have woken up, seen the bottle, and had a try. Not saying that was what happened, but it was an interesting development - away from"you gave them the drugs" to "were there any other drugs, apart from those you gave the children, in the villa".
Wouldn't have been the first time that has happened - but still doesn't make sense of why they would make-up a cover story.
And if the father is telling porkies, he is a fucking good actor