I wish I had your problems - thinking of things to do in Honolulu!!
We have been to Honolulu three times and have had some pretty good meals there. We had a great lunch at the Hau Tree Lanai (I think in the New Otini) near Diamond Head. The food was great, and it is on the beach, so you can get some oggling in. If you are there, stop by and visit the Honolulu aquarium. It is small, but is one of the best we have visited. (You can also pick up an Entertainment Book for 2-fers there).
At the low end, we have had good meals at the Shore Bird Grill - a cook-your-own place right on the beach, and we enjoyed the Hard Rock Cafe.
I respectively disagree with Hi-Guy about the ease of hiking up to the top of Diamond Head, but it is definately worth it. Just do it early in the morning while it is still cool.
The Polynesian Cultural Center is worth going to - I think it is open only in the afternoon - but get the "good tickets" with the Luau and good seats at the nighttime show. It is spectacular.
Enjoy!

DD