The art and cultural tours of Aulani are a must-do! The storytelling created within the resort is phenomenal and easily overlooked if you don't know it's there.
The free morning fitness classes are actually great quality as well. I found them both fun and challenging, and suitable for most fitness levels.
Another vote for shave ice!
Watching the fish feeding at Rainbow Reef was another fun event we tried to do each day.
Movie rentals! You can rent DVDs (for free, two at a time) in Pau Hana room and bring them up to your room to watch in the evenings.
Duffy and ShellieMay - This is the ONLY place in North America where you can meet either of them. I love them so much! And now, 'Olu is at Aulani, too, though not ready to meet guests yet.
'AMA'AMA dinner at sunset