We did it 2013. Our goal was to do the waterfall hike at the "end of the road" at Kipahulu National Park. So we skipped most of the stops on the first third of the drive hoping to stay ahead of most of the tourist cars. We had picked up sandwiches in Paia and were on our way before 8AM. This worked very well, and we didn't run into crowded pullouts. We used the Maui Revealed guide to decide where to stop.
Our first stop was #11 Haipua'ena Falls. After crossing the road, I think we walked a couple hundred meters to see the waterfall.
2nd stop was Kaumahina State Wayside. They have bathrooms. There are some short trails, but I don't remember anything too spectacular.
3rd was
Ke'anae Peninsula. This is a short drive off the main road, but once you reached the parking lot, I think it was a pretty short (maybe 3 min), and flat walk to the beach where you could see where a lava flow had come. I don't quite remember how much you can see from the parking lot. Looking at Google Maps, it looks pretty close
https://www.google.com/maps/place/Ke‘Anae,+HI+96708/@20.8599481,-156.1442608,51m/data=!3m1!1e3!4m5!3m4!1s0x7954b4ad34ca4625:0xc88bb64d2da938e4!8m2!3d20.8590307!4d-156.148795
The book says there are two easily visited small waterfalls at Pua'a Ka'a State Park, but I don't remember the details.
We stopped in Nahiku, there are a few shops including a nice art gallery, and a supposedly pretty good Thai restaurant. While we were in the art gallery, Weird Al came in with his daughter looking for directions to the "watering hole the locals swim at." My DH didn't notice, and was wondering why I was making a bunch of gestures.
There were also several "on the side of the road" pullouts that we stopped at just to look at the vegetation and cliffs, but I don't remember where each of those was.
One of the highlights was the black sand beach at
Wai'anapanapa Park. The beach itself, is down the cliff, several hundred meters, I think that path was actually paved (until you hit the beach) but it was pretty steep and not the best pavement, so I wouldn't recommend pushing a wheelchair. But there is a parking lot, and I think paved walkways to overlooks. Let's see if this Google maps link works, to show distance.
https://www.google.com/maps/place/M...3e741dc113e7f!8m2!3d20.7983626!4d-156.3319253
In Hana itself, Hasegawa's General Store is supposed to a kick, just to see the variety of different things they stock. We were too tired after our big hike to want to stop, so I don't know if that's true.
At Kipahulu, there is a small visitor's center that is easily walkable. The Seven Sacred Pools is where most people go, but that is a bit of a walk. Oh, looking it up on the NPS website, the pools are closed indefinitely due to rock slides, so you wouldn't have to feel bad about missing them.
The two bolded areas are the places we enjoyed the most, that I think should be manageable. But the road really is beautiful and unique. My DH and I grew up in the PacNW and there is a famous road their called Chuckanut Drive. A bunch of car commercials get filmed there. So we were quite familiar with tight, twisty roads, high on a cliff with water down below. So we didn't have quite the white-knuckled experience that everyone described it as. The one lane bridges were new though. On our way back up, we left after 4PM, so most of the tourists were ahead of us. No one was on the road but locals and we had an absolute blast driving it as fast as we could (although the locals were going faster than we were).