Haleakala Sunrise - be sure to bring a blanket or jacket. It will be cold.
Eat at Da Kitchen. If you are arriving in Maui and have not eaten, it is right by the airport. I had the Notorious B.I.G. Moco and it was delicious. Everything there is good.
http://dakitchen.com/food-menu/We went on a few excursions and really liked Trilogy Excursions. The Lanai trip was a nice full day event, but you don't get as many fish. The Molokini trip will have more fish and a lot more tourist.
Lanai -
https://www.sailtrilogy.com/tour/lanaiMolokini -
https://www.sailtrilogy.com/tour/molokiniIf you want to snorkel on your own, Honolua Bay and Kapalua Bay are great. Be sure to check with your snorkel rental to determine the place with the best conditions. Rent from Boss Frogs (and also rent the underwater camera from them).
Mama's Fish House is great. Be prepared to pay a bit more. Dress code is all over the place.
You can eat at Mama's after the Road to Hana. Be sure to pack food/drinks for the road. It is long and tons of turns/1 car bridges. We drove the road with a CD that gave us history and tour stops. BTW, don't forget gas. If you can get a hybrid car.....it will last quite a bit of time.
We really liked the view at Duke's Beach House. Try to get a table around sunset......and make a reservation!
If you just want a burger one day......go to Teddy's Bigger Burger. It is like 5 minutes from your hotel.
We did the Drums of the Pacific Lu'au. Our travel agent got us a buy one get one free ticket, which was nice. We upgraded to VIP (don't have to wait in the general admission line) and really enjoyed the show.