Thanks y’all. 
Since as described in the OP the ‘children’ are adults of an age of legal independence, I would not feel comfortable ‘demanding’ they obey my commands.
I may exercise my ability to have a rational conversation with the child regarding their choices, both to enhance their understand of their actions and my understanding of their actions.
I am the biggest fan in the world of creating win / win situations, and making something good out of whatever life hands you, so that is what I would strive for.
And no, I did not look at the example art, partly because I am at work and partly because I believe in my argument of rational steadfastness does not hinge on the individual nature of the art described.
In the end, if my grown children would want to engage in some activity I was morally or tastefully uncomfortable with, I would have to conclude that I had already failed during the time I was raising them. At this point other than some gentle, considerate conversation, I am honor bound to let the chips fall as they may.
I had my chance years earlier to try to instill the values I hold dear. I lose.
I’d be ok with it, as long as I never, ever saw the pictures.
A failure of yours? Other people have minds of their own and can choose how to conduct theirselves. If a child of yours chooses something else, it’s not a failure on your part. It’s their free will.
the answer is still no.
I’d say not a big deal.
This was actually a situation that came up frequently in my college days.
The art department paid nude “life study” models very well. They paid $20 for a 50 minute session, this was in 1975 and the other work available for students paid about $3 an hour (to put it in perspective a student could purchase an ounce of weed for $15 at that point in time .)
I had two female friends that did this on a regular basis and neither of them was a conventional “hottie”, this wasn’t Playboy type stuff…one was rather plump and the other one was really skinny…that said, one of the girls was a bit of an exhibitionist and maybe liked the gig a little too much, I think she got reprimaned once for wearing a garter belt to a session, although the students in the class dug it.
Local legitimite advertising agencies also went through the theater department at my college to procure nude models for advertising…these were usually trade ads, I remember one for stadium seats and another for some commercial construction equipment. These were very professionally done and a university theatre department rep was present at all the shoots.
These gigs were also really high paying, a student making a couple of hundred bucks for day’s work was practically unheard of and REALLY GOOD pay for the model…this was why the college was so supportive.
So, mayybe it’s my liberal 70’s upbringing but I don’t think it’s a big deal at all.
I would very actively and very LOUDLY oppose it whether my child was male or female.
I don’t think posing nude is morally wrong per se. Sometimes nudity is art, sometimes it’s just plain porn. Either one, though, could put their future career at risk, which is why it’d be a HELLZ NO.
What if the child is planning to be a model in the first place?