I'm not sure if they would ship it to you on Maui. They do charge for shipping though so, I'm not sure if you'd want to go that route.
I recommend the Chanel at Ala Moana. I believe their selection is just as good, if not better than the Waikiki Boutique. Also, right across from the Chanel boutique in Ala Moana, there's also Chanel fine jewelry. If you're interested, there's also a 2 story LV, Cartier, Harry Winston, Tiffany's,
Prada, etc., all in the same vincinity in the mall. Shopping in Waikiki is too spread out and it's not like you can see the ocean from where the shopping is in Waikiki.
In the mall, if you decide to grab a bite, you can have lunch at NM and have a view overlooking the beach. NM service is slow so I wouldn't recommend eating there unless you have a 1.5 hours for lunch. Also, I recommend their food only b/c of the view, the food itself isn't that great. If you leave no later than 3:30, you should be fine. Also, on your way back, getting thru security should be easier since the inter-island terminal is just before the main terminal, so you won't be stuck in the longer lines of the main terminal. On your way to the mall, check out if there are signs for road construction or if there's any roadwork, if so, then definitely by 3.
Have fun when you reach Maui. I'm not sure where you're staying but if it's in Lahaina, be sure to explore around and outside of Lahaina. Wailea is stunning and Makawao is a very hip place for a nice dinner. Also, I don't know if Maui has a Chanel, but if so, the tax on Maui is a little lower. The tax on Oahu is something like 4.71%, while I believe Maui is still in the 4.167% range.
Are you sure, you don't want to just go to the mall, enjoy the shopping (maybe not buy Chanel) and then when you go back home, order your items from Bergdorf? I order from there since there's no tax, I can use my NM card, and I don't get charged for shipping.