congrats
we honeymooned there 16 years ago
I played Princeville while she did the spa, I would definitely play Kukuiula
the Princeville hotel works well especially if you want easy access to the Hanalei Bay area with some nice sunsets and view over the bay from the hotel to the volcanic mountains and the beautiful Napali Coast
paddleboarding is very popular in Hanalei
I have not stayed on the Poipu side so that would be different from a dirivng standpoint
we hiked the trail on the Napali coast from Kee' beach and I think I can still smell the fresh Guava
we definitely drove quite a bit on the road around the island
I think the closest Starbucks from Princeville is in Kapaa
definitely do the helicopter
there are bugs/mosquitoes in the evening
The Ultimate Kauai Guidebook is a great guidebook
trust your friend and have a great time
and the curveball I would do is to fly to Lanai and stay at either Four Seasons hotel and play golf at both courses there