Are you talking about hiking/camping Kalalau trail? Or are you talking about camping at Polihale?
Kalalau you def. need permits and honestly its a tough trail when its wet, and its been really, really wet lately. It has been completely closed various days over the past couple weeks.
You can camp at Polihale if you want fairly easily (you should get a permit, but many people don't). That's still Napali, but you can drive in and choose a campsite. (4x4 is prob. needed, we were out there this weekend and the road is super muddy and awful)
Either way the water and kayaking is a no go unless you really know what you're doing (no offense, but it sounds like none of you do). Even then, nobody on Earth is even trying to land a kayak in winter. The swell is almost never below what would easily kill an inexperienced ocean goer from Dec-Feb.
Hopefully your friends get warned or wake up, otherwise they are really risking their lives.