My wife and I did the same thing a couple of years ago. We got certified here in the NW. With our open water dives at Hoodsport. We also did a dive boat trip with Bandito's in Puget Sound the week before we went to Hawaii. We each had 8 dives when we went to Maui. We had planned on doing a lot of shore dives, but there was a south swell (~8') that ruined that for us. We even had some shore scooter dives booked, but they were cancelled due to the swells. Our first and only shore dive was at Turtle bay (i.e., Kapalua bay). Which is great for beginners, because it is somewhat protected from swells and current inside the bay. I saw two green turtles at the cleaning station near the opening of the bay. I wished I would have had a camera! The parking there was tight; so, get there early. The Maui Dive Shops are a great resource. We rented our tanks, weights, and dive flag from them. At turtle bay, one of the Maui Dive shops instructors gave us a tip on parking there. We parked on the shoulder, and partially on a grassy area, near the restrooms. We only got a warning like he said. One thing to keep in mind is to not gear up in the sand. We started to gear up on the beach, and I quickly realized the hazard of getting sand in the connection points of the regulators...so we moved up to the grassy area. I noticed other divers were gearing up at their vehicles, and then trekking down to the bay. Which is a walk that my wife would not have liked that at the end of the dive.
The rest of our diving was with Lahaina Divers, and we loved them. My favorite dive was Molokini Crater. The visibility was 180+ feet even with the south swells. The area is protected from the southern swells due to the crater. It was like jumping into a fish bowl, and the deepest I went was 80'. Of course you don't need to go that deep, and most divers didn't. I had a tendency to hug the bottom. When I compare all of my 100 dives, Molikini is number one to date. I know there are probably bettter dives out there, but I haven't been there yet! We also dove the Catherdrals, and that awesome too. Like others have pointed out, the diving in warm water is so much easier than the colder NW waters.
We also stayed in Kihei and did the drive to Lahaina. Planning one hour for the drive to ensure that we got there on time. Since we were doing multiple dives with Lahaina Divers, we left our gear at the shop. Which was great not having to pack it back and forth every day.
Happy diving.
James.