Can't recommend KR Campers highly enough as a way to experience Kauai. Jeni (our point person while on island) made sure to prep us well for rooftop camping and gave us many pointers for gorgeous places, good food, groceries, etc; the whole team was incredibly friendly and warm and available for questions whenever we needed them. Setting up the rooftop tent seems intimidating but they'll talk you through it, you'll be a pro after your first night! The kitchen kit was terrific and the linens were comfy.
Would recommend adding:
-Camping pads: the built-in mattress in the tent is fine but extra padding helps
-Pay for the ride to and from the airport!! No Ubers on Kauai.
Some things we found handy to add to our supplies:
-Cooking oil
-Ice
-Plastic containers for leftovers! Big portions from island takeout.
-Earplugs (the rainfly is heavyduty so it's loud in the wind)
-Cash for car wash and vacuum (requested by KR before checkout; on-island car washes don't all take cards): $20 or so