I've read the following, and enjoyed them (can we have some more, please?) and wonder if there are more in the same vein and of the same quality? I'm not fussy about age either way, but do feel that, with the progressively earlier onset of puberty, imposing a post-pubertal age limit is unrealistic.
Fanlon's Windy Pines
John Evans' Diary of a Masher
OmegaPet58's The Blender
Nick Scipio's several nudist camp series
Alured de Valer's Best Summer Ever
While I liked those stories, those 'nudist camp' stories were clearly written by those who'd never actually visited one, as I've always been a nudie myself. The whole vibe is significantly different than the stories' presumptions. As generally, it's a lifestyle, not a swingers' camp. And while there are hookups, they are usually kids present too (i.e. small children).
So, those stories are enjoyable escapist fiction, they're as far from actual fact as it's possible to get. And while Americans have virtually no concept of nudism, even the few U.S.A. locations (rarely actual camps, more often they're simply unofficial sites where Europeans frequently gather) are considerable different.
And yeah, I've discussed it with them, yet as always, their answer is "Who cares, it's a damn story dude?"
And in my case, it's never been the sort of story I was inclined to write anyway.
Murray Wilson has two series of 10 stories each that both involve large scale nudism. Both series are mostly separate stories in a shared universe rather than telling a single story across several books.
Blanke Schande College is about a university that require all female students to be naked.
https://storiesonline.net/universe/1185/blanke-schande-college
This Naked World involves a global push to adopt "Lifestyle Nudism" as a protected way of life in many countries.
https://storiesonline.net/universe/1186/this-naked-world
Neither of the series is specifically family oriented, but BSC has a few incest stories and TNW has it in most.
As an aside, puberty actually doesn't start earlier today than it used to, but it does progress more slowly. This is mostly due to poor diet and child labour historically. So puberty began at the same age a thousand years ago as it does today (10 - 12 for girls), but certain key milestones happen later, especially menarche.
If you're interested, here's an article about it: https://theconversation.com/children-arent-starting-puberty-younger-medieval-skeletons-reveal-91095.
As an aside, puberty actually doesn't start earlier today than it used to, but it does progress more slowly.
According to the study recounted in the article, puberty progresses more quickly now than in the Middle Ages. Specifically, girls reach menarche at an earlier age now than before.
Melissa's Secrets by Pookie. It's a long series but worth it. Only blight is that it's not finished.
Beth by Bronte Follower fits but was removed by the author. His New Tree also fits but was removed.
There is a section of Beth for sale on zzBookstore and he is reposting the story on another site.