Just returned from Maui. Great vacation. Its very wheelchair accessible. We stayed in a 1 BR condo in Kihei - complex is called Hale Kamole. It was just a regular room, but was quite accessible. The whole complex is accessible = pools (2), tennis courts. Beach is right across the street. Not the best access for sand, but lots of grassy areas. Only problem with condo was the tub - it had a sliding door with the tracks that are hard to transfer over. Just used a folded towel to protect the butt.

Best thing we did was Blue Water Rafting. Whale watching and snorkling on a 30' ocean raft that seemed to be able to handle any surf conditions. The crew (Captain Jeff and 1st mate Scott) was awesome. Hauled me in and out of the boat for snorkling. Really a great outing, I highly recommend it. But you need grip and arm strength to hang onto the boat - its quite the rough ride. But nothing gets you closer to whales and lava caves. Bring something warm, a big towel, and ask for a rain coat in rough water (even if its not raining). Cause you can get soaked.