Aloha Lionel! The Kalalau Trail is an incredible experience. You will need a permit from the Hawaii DLNR for both the day hike beyond Hanakapi’ai and for overnight camping. The trail can be challenging with steep sections and stream crossings, so good fitness is important. With a 14-year-old, it is doable if they are an experienced hiker. Start early, bring plenty of water, and pack proper gear. You can explore Kauai activities and guided options here: https://www.hawaiiactivities.com/en/hawaii/kauai/ctg/190102:kalalau_valley/?utm_source=travelguide&utm_medium=comment_reply&utm_campaign=comment_engagement&utm_content=kalalau-trail