There's always discomfort when the subjects of a picture don't fully understand the implications of display. This question arises, in a different way, with projects involving Alzheimer's patients. While, for Emilie and Michael, the shoots for Untitled were doubtless innocent fun with mum, you wonder about their reaction as teenagers and adults to the realisation that they have been displayed naked around the world. That isn't a police matter, but it's an important moral one. But history shows that the children of artists suffer one way or another.
Novelists cannibalise their offspring for plots and dialogue.
The children of photographers and film-makers endure the same process but with less possibility of disguise, unless mum or dad is into abstracts. But the policing should be left to Brian Sewell, not the vice squad. You feel that the time of the filth cops would be better spent online or in Soho than in Hampstead.