Consider renting a car for the Road to Hana tour and Haleakala National Park. Uber or taxi are recommended during nights out or when alcohol is involved. Air travel may be required between islands, with costs varying based on the carrier and schedule.
If you have more time, consider adding a hike to the Manoa Falls or visiting the Polynesian Cultural Center. For those with less time, eliminate one of the beach days or shorten the Volcano National Park visit to fit personal preference.