On the Big Island, I wouldn't recommend the Mauna Kea Beach Hotel (Autograph Collection). It gets great reviews, but my family's stay there last year convinced me that the reviewers are remembering greatness of decades past, not the current condition of things.

On Maui, you can't go wrong with either the Ritz-Carlton or the Wailea Beach Marriott Resort. If you take my advice and book them into the Waikoloa Marriott on the Big Island, maybe the Ritz would be something a little different and more secluded for the Maui portion of the trip. That being said, I personally love the Wailea area and have had many spectacular stays at the Marriott.