thanks to all who have posted with suggestions.

I will plan to go to the Arizzona memorial and climb Diamond Head.
I will go to the north shore (rent a car for one day) to see the pipeline and include a hike or maybe rent a mountain bike for a trail ride.
I still want to snorkel but the comments about Haunama bay have been decidedly mixed, probably more on the overcrowded, not so good side.
On Firday early I will fly to big island early, rent a car and go to VNP. Will stay at volcano house. Will hike a lava field, and try to take in a forest-type hike as well. Maybe find a waterfall?
Saturday evening, I'll fly back to HNL and a couple hours later board my flight back to mainland, work, snow, all that stuff that I'll try not to think of for the seven days I'll be there.

Any last minute comments/suggestions?