@mickEblu the Road to Hana is nothing like our CA windy roads. It’s very narrow and if there’s any traffic you will move slow. Like slower than CA traffic slow. Hawaiians drive slowly on paved roads, even the “highways”, but locals and tourists will drive barely at all on the Hana Hwy. Don’t even consider it unless you leave really early to avoid the traffic. I last did the Road to Hana about a decade ago because there’s no way I’m doing it with my kids. On our last trip in May we decided against it and they’re 8 and 6. Maybe consider it if your 3 year old is REALLY good in the car otherwise it’s just not worth it. Especially with a 79 year old getting really bumped around all day. It’s an all day trip. It really is not worth a day out of your trip if you don’t have that many days there. There’s a reason they sell those I Survived the Road to Hana shirts.
The reason I asked about what you want to do is that going anywhere on Maui can take up a lot of time so don’t forget to take enough time to just relax. I really liked the apps they have for Maui that will narrate for you as you drive. I’ve been going to Maui my whole life but still learned a few fun things. That will also point out different places you could consider going. The Iao Needle is a very pretty spot and easy for everyone in your party. Upcountry is also beautiful if you want to take a drive. I would definitely skip the crater, a long windy drive with an unreliable pay off. It could be so cloudy you see nothing.
If you live near any aquarium skip the one in Maui. Unless your child really loves turtles there’s just nothing there.