Be sure not to rent a car that is not t the airport, but a shuttle away since you'll loose time. If you just want to browse at a shopping center, there is one right at the airport. Iao valley is stunning, but be sure to hike the trail with your valuables, since they can enter a trunk in 1-2 minutes!!!!
Don't leave anything of value in the car.
The asquiarium is amll but very new. Iao Valley has a 10-15 minute slow easy hike, but if you're in good shape you can do it in less time. The park also has below it a unique little "decor" of various ethnic groups who came to Hawaii that you could take pictures of. You could stop by a local grocery store on the way and purchase the flowers called protea that only grow on Maui that you could take home and then dry it. It will last forever if you dry it upside down, as normal.
You can also buy anthuriums, but it would cost a little more. Maui is known for its flowers as well as wonderful food -- guri guri ice cream (like a sherbert), potato chips, and Japanese food. Wow -- so many choices but so little time!!!

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