I think you're landing too late to do the Arizona memorial the first day. If you can, be there first thing the next day to get a ticket, if you can't get online in advance (try exactly at 7 am HST day before you want to go, which is when additional tickets are released, or have someone do it for you if en route). It's a bit of a pain to get tickets so late...
If you decide to do Diamond Head first day, calculate how long it'll take you so you'll be back before dark, or be prepared to hike in dark.
If you want a great view of HNL and Diamond Head, drive up into the mountains. There are some nice pullouts. Check out
@PBaruch's TR for a photo.
Remember that HNL is a city. Driving there feels like NYC. Definitely get a car, but don't drive to your hotel until you are DONE for the day. Driving from the airport to Waikiki, if you stay there, is awful. You'll wonder if you're actually in Hawaii.
All Dan mentioned sounds good.