There has always been an additional person / child charge (above what the room charges are for two adults and one child, i.e; standard occupancy for BV, WV, SWV, DWV & PWV at Rangali) but I don't think they've ever charged them to people booking directly through the website or Hilton call centre. The pricing has always been seasonal and it is higher over Festive Season. I've always seen it on their website when making a booking and they listed this charge in their Best Rates PDFs but they haven't done those for a few years now. The only difference I'm seeing here is the age where it was 12 but now 14. They may have decided, as you've hypothesized in point #3 in your post, to actually implement this charge during Festive Season.