We didn't stay at Turtle Bay, but its no doubt a beautiful resort and a great location for the activities you referenced. We opted not to stay there during our trip because the immediate vicinity seemed a little isolated, similar to Aulani. And when we traveled in September, we found the waves too rough and high in the North Shore to be swimmable. I am not a strong swimmer, so the only "ocean" swimming I was able to do anywhere was in the lagoon at Aulani.
Just throwing it out there, but have you considered a night or two in Waikiki? The area has a very different vibe than anywhere else in Hawaii. Lots of things are walkable, and many tours (with transportation) are offered from hotels in this area. We opted to stay in Waikiki at the start of our trip, which we enjoyed because we were adjusting to the east coast time difference then. A lot of places were open in the wee hours of the morning when we were wide awake during the adjustment period. We also did Pearl Harbor and Diamond Head during that time, which are best done early in the morning. We did these as tours from Waikiki which worked out well. Lastly, we chose not to have a rental car during this time to avoid the additional rental cost as well as parking costs/hassles. We were able to easily walk to many places and also use the trolley to get up and down the strip of Waikiki.
