For Hyatt, I would recommend either the Andaz on Maui or the Grand Hyatt Kauai. As a Diamond member, you can use one of your Tier Suite Upgrades to get a confirmed suite, and the resort fee is waived along with other Diamond benefits. I was at the Grand Hyatt two weeks ago and think it might be what you are looking for.

Here are the existing threads in the Hyatt Forum on these properties that you can use for more questions/information:

http://www.flyertalk.com/forum/hyatt...er-thread.html
http://www.flyertalk.com/forum/hyatt...1-forward.html

I am excluding the Hyatt Regencys in Waikiki and Kaanapali as they are in busier, touristy areas but they also have rooms with great ocean views.

For Hilton, I suggest you look at the Grand Wailea or Hilton Waikoloa Village for the Diamond benefits there:

http://www.flyertalk.com/forum/hilto...ort-us-hi.html
http://www.flyertalk.com/forum/hilto...age-us-hi.html

I am excluding the Honolulu Hilton properties for the same reason above. I drove by the Hilton Garden Inn on Kauai and noted it's location and decided it wasn't that appealing to me.