Pro tip for Haleakala: the sunrise is really, really cold. Also, the traffic jam to see the sunrise has gotten out of control over the past two years. Last I heard, they were considering a permit system for sunrise passes, because there were literally over 1000 cars per day showing up for sunrise. If you really want to see it, you need to wake up at around 1-2 am and then drive the extremely windy, insane road in the dark and then sit in a giant line of traffic. THEN, (if you're lucky and can find parking) you get out of your car and it's below 40 degrees Fahrenheit, and you didn't plan for that because Hawaii. So you hop around, trying to keep warm, and watch the sunrise, or you cry uncle and climb back into your car with the heater on. I realize that mainland people don't always think 30-40 degrees is that cold, but I've long since acclimated to Hawaii and brrrr it's horrible.
Personally, I think the Haleakala sunrise experience is overrated. Here's what you do: sunSET at Haleakala. Way fewer people and just as pretty. Also, you can do part of the Sliding Sands trail, which is super cool (you hike into a volcano crater and it's really neat), and then hang around afterward for the sunset. Fun! If you like backpacking, there's an incredible loop trail with two amazing backcountry campsites, but most likely that's not your thing.
Another pro tip: if you want to do the crazy bike tours down Haleakala, it's fun but fairly dangerous. And if you do the sunrise one, they rush you down the mountain (which is part of why it's so dangerous). What you do is go AFTER the sunrise bike ride, which is nice and uncrowded and for some companies cheaper, and they let you take as much time as you want. And there's lots to see while you bike down: Kula, Makawao, the lavender farm/garden. Make a whole day of it. Even in July it's generally pretty mild, or at least not unbearably hot. This is a really nice day excursion.
I hate Hana but that's because I've been there four times and I'm over it. You kind of have to go if it's your only time. I guess. If it's between Haleakala and Hana, do Haleakala. Reasons I hate Hana: Horrible traffic, horrible carsickness, a couple of waterfalls but meh, horrible traffic, meh restaurants in Hana. BUT there are some cool hikes. I second the advice to get a VRBO in Hana, or you can camp at Kipahulu National Park (it's in Hana and also is where Charles Lindburgh is buried), which is buggy but pretty beautiful.