Must sees: Hana and Haleakala. Each of these are big trips so I wouldn’t plan anything else that day:
Haleakala Sunrise http://www.nps.gov/hale/index.htm. If you have a NP card you can use it there. Plan to get up around 3:30am and drive about 3 hrs. from Lahaina or 4am and 2 ½ hours from Wailea. Bring a jacket or blankets; it’s chilly at 10,000+ feet. If the weather is bad, forget it and go another day. You might also want do a downhill bike run instead, there are several companies Otherwise, after sunrise, go to Kula Lodge for breakfast, then head over to the Piiholo Zipline www.piiholozipline.com in Makawao, or Tedeschi Winery in Ulupalakua www.mauiwine.com. The views are gorgeous and there are places to stop and have a burger or salad and picnic outside. This is also the backside of the Hana drive, which is a full day. Leave early say 8am from hotel, plan to drive about 4-6 hours, pack a cooler with drinks & snacks. The road is winding and narrow so be careful, but the scenery is amazing, lots of waterfalls along the way. Stop in Hana town, there are also CDs you can take in the rental car to help you with narration along the way. You can visit the Seven Pools (Oheo Falls) in Kipahulu which is also part of the Haleakala NP. Return the way you came, or continue around the island coming back to Ulupalakua upcountry and head back down to Lahaina.
Do try the Trilogy Excursions for snorkeling or whale watching (in season) www.sailtrilogy.com either out of Lahaina or Maalaea Bay. Take a day car trip to Kihei/Wailea/Makena for swimming, lunch, shopping. Stop at the aquarium www.mauioceancenter.com, it is really one of the world’s best. Head on over to Kihei passing through the Kealia Pond National Wildlife Refuge, a bird sanctuary, and drive through the 6 mile long town of Kihei on South Kihei Road. There are marvelous white sand beaches to stop and enjoy, as well as world class restaurants serving up local specialties & fresh fish. Head to Makena with your snorkel gear (rentals are everywhere, and cheap) be sure to take some fresh water and snacks. The road ends at the black lava field after Makena, there are short hikes to La Perouse Bay, but be careful as it is hot out there.
If hiking is your passion, contact www.hikemaui.com for the best information and guides – lots of off the beaten path adventures. For surf & SUP lessons, contact www.actionsportsmaui.com located in Kihei, go early morning before the wind comes up and learn to really enjoy the water! Be sure to make dinner reservations at some of our finest restaurants to sample fresh fish, locally sourced produce as well as home-grown beef & fresh brewed beer.
Lots of things to do on Maui, some are free, and some have fees, but all guaranteed to make your vacation fun. Have a wonderful time in Maui!