bitter1,
Buy a copy of "Maui Revealed" when you get there. It has a lot of good info in it on places, things to do (or avoid), and good directions on how to get there.
When you are staying on the Kapalua side, my favorite snorkeling spots are Kapalua Bay, Honolua Bay (just north of there), and Black Rock (a few miles south.) There is a nice hiking trail that follows the coast from Kapalua Bay up to DT Fleming beach that is a scenic and mostly flat hike. Another short drive and hike that I liked on the north side was going to the "blowhole" where the tide is forced through a volcanic tube to create a giant geyser. My favorite restaurant on that side of the island is the Sea House at Napili Kai beach (right next to Kapalua.) Great location and good food at reasonable prices for breakfast lunch and dinner.
Another excursion that I can recommend is taking a boat trip to snorkel at Molokini crater and/or the island of Lanai. I went on a Pacific Whale Foundation boat and they did a good job. There are other companies that do this too.
When you are on the Hana side of the island, I strongly recommend the Pipiwai trail hike above the Seven Sacred Pools. Many people say that it is the best hike on the island. It is 2 to 3 miles of climbing on a well marked trail that takes you through a lot of varied vegetation including giant Banyon trees, a Bamboo forest, and bridge and stream crossings to see various water falls and pools. I did it successfully in flip-flops because it wasn't on the plan to do that day, but I would recommend some more substantial shoes because the trail has a lot of rocks and tree roots that can trip you up.
If you want to splurge on a great dinner, try Mama's Fish House near Paia. Check it out online and make reservations if you decide to go.
Enjoy the trip. Two weeks will go fast once you are there.
Phil