i just don't see where the choice
i know i'd hate my mum and dad if they took me to a nudist resort - what ever age i was at, be it 8 or 15. you are kind of working on the assumption that the people there are consenting to be there - that the younger family members have not raised objections, what if those objections have been ignored? kinda reminds me of the old "what? my child can't swim? well then, let's throw him into the deep end until he learns how to" attitude. i'm not saying you have that attitude, but if the parents have no problems with nudism, and want to go to a nudist resort - but the child objects, but has no say in the matter, but is taken along anyway - where is their protection?
for me, it really does just boil down to choice - and i don't think anyone under 16 is able to make the choice to go nuddy or not. i'd just rather be safe than sorry.