Been to Maui twice. 2009 and 2019. 2009 we squeezed in a lot. Road to Hana, Old Lahaina Luau, hit several beaches, took surf lessons. Loved the hell out of the road to Hana. We had an accompanying CD or App and it was great. Started off eating at Charlies. Supposedly Willie's favorite place to eat. Saw all the falls. It was June, so probably not as flowing. I recommended picking up a Frommer's Guide for Maui. There are some cool unknown spots along the way that the FG points out. Black Sand beach was most memorable. Water was coooold.
Rental car...I pulled of a 30-35 dollar a day Toyota Mini-Van rental. Priceline was the shit back in the day.
The only thing we didn't do was sunrise at Haleakala, but we did that in 2019. It was foggy at sunrise and raining. It was still an experience since we were there in the Summer and it was cold up there as well. We got to stay in the Marriot Resort on Ka'anapali. Wife and I just chilled there and at the bar and pool.