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We go to Hawaii every year- go to Maui, stay in Kihei if you're on a budget, but Kaanapali over in west Maui is going to have more kids-oriented activities/resorts IMO. My wife and I stay in Wailea every year, which is nice, but if we took our daughter, who's 2, we'd probably stay in Kaanapali.
Although, if you got the cash to burn, the Grand Wailea would be, IMO, the BEST choice for a family. Private beach, and more swimming pools than you'll have time to use. We go to dinner there every year and we see toddlers playing in the kiddie pool well into the night.
As for the road to Hana, if you want a test run, do the west maui drive, a lot shorter with plenty of incredible views, and if the family does ok with that, tackle Hana. And yes, rent a car.
Seriously, there's enough to do throughout the island that you won't get bored, and your daughter will have a blast playing on the beach.