This question already has an answer here:
When a children appear in a movie that has a scene or two depicting sexuality (R rated material), is it the norm to let these children know what kind of movie they are participating in? Or are they kept in the dark until they grow up and find out?
What if they wanted to see the movies they acted in? Are they even allow to watch the full R-rated film they helped make?
Is there any kind of formality or agreement between the child and the movie/TV-show producers/directors, in which the child's approval is obtained? Or is it the parent's approval that counts?
Case in point: In the movie Ken Park (2002), we see a little girl watching something inappropriate on TV (maybe she was not really watching anything, and they edited it out like that), but the whole movie is R rated and is inappropriate for ages below 18 to watch. Does the actress child know what kind of movie is she in?