Given your criteria, I recommend Kauai and especially the North Shore area. You will need to find a host or camp (I recommend Anini Beach Park) if you want to avoid the resort hotels.
You might consider the Paia area of Maui as well.
When are you coming?
Yes i will arrive at kauai on the 12. April. And After 10 days i go to Big Island. You can join me if younwant :)
Guten tag Frau Ott.
I'm a bit biased, but really like Oahu's Northshore. We have wonderful beaches, great waves, and easy access to the city (Honolulu) for shopping and activities if/when needed. Insure you'll have a great time regardless which island you choose. If you swing by Haleiwa/Waialua area, hit me up and Nugget and I can take you out for a paddle on the Anahulu river.
Most people who are looking for a more authentic hawaiian, relaxing, non-touristy destination in Hawaii are delighted to find the island of Molokai to be just what they need. check out visitmolokai.com for more information.
Just ask me and I will lyk, I lived here all my life and work in downtown/waikiki so I know the areas really well, generally speaking you have to get out of town or another island to get to non touristy spots, so if you are staying Oahu n Waikiki its a far trek, i'm also a big foodie if you need food ideas =)
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