I really liked hiking the Na Pali coast in Kauai.
In Maui I thought the sunrise at the volcano / bike ride down was overrated. If you are going to Kauai, I think you can skip the Road to Hana - the whole island of Kauai is like that. But I feel like these two are very popular things so you should do them if you want - I don’t want you to miss out bc I said so in this post