And I don't quite see your point about your kids' friends using iPhones. I sure as hell wouldn't give a kid a "luxury" phone. I'd take the cheapest thing that does the job and lasts a long time. An iPhone has a very long software support window so the cheaper models actually end up cost-competitive with budget Androids.
As for folds and flips, I've mostly seen people in suits using them, along with a few techy power users and some kids with rich parents. That's a luxury phone in my book.