Hi to everybody:
Thank you for all the information. I have read carefully each message and I am traying to make the best decisions. I got fast and properly feedback from the staff of Sheraton Keauhou (very kind people by the way, at least by mail), so its most likely we will stay there.
Yes, it will be better if I could stay a couple of days more, but as far as I am flying with miles, I had to stick to the flights where there are seats available to use with AA miles.
Instead, I will stay 8 days in HNL, so while I am planning the Big Island activities I start to organize the stay in Oahu.
And yes, I like to do the dolphins experience. I will get to you in the following days.
Thanks again to everybody. If you have any new idea or any other advise it will very welcome.