I would recommend:
Haleakala Crater - It's a long drive, but worth it. I have been up there for sunset and also for sunrise. There is a place where you can park and walk around. There are no food options, so bring snacks if you plan on being there for awhile.
Road to Hana - You can drive it yourself or go on a tour. I have done both. I get car sick, but the road never bothered me because we made a lot of stops. If you plan on doing this, you might want to look up some information about the best places to stop. If you do a tour, then you don't have to worry about driving or figuring out the best places. The road is very narrow and winds around the side of a mountain. There are a lot of blind curves. My husband had no problems with the drive, but it's not something I would do myself.
Molokini Crater - Snorkeling. That was a great experience. The water is so clear and you can see so many different types of fish. On one snorkeling trip we took, we went to the crater and then to another area where I saw more dolphins than I had ever seen in my life. It was an incredible experience.
We've also done jet skiing and riding ATVs. That was fun. We did a submarine tour, but it was terrible. The visibility was poor and it was a waste of money
Helicopter tour - The absolute best experience of my life. They took us places that you could only see by air. It was amazing.
Lahaina - Definitely worth a visit. It was a fun place to shop and walk around town.
There are many very nice beaches. There is a nude beach there. I think it's called Paia. We discovered it by accident while walking along one of the beaches. We climbed over some rocks and
Our son was with us, so we turned right around and went the other way.
I love Maui and wish I could life there.