If you have a rental car, you might seriously consider changing your Molokini charter to one that goes out of Kihei. B&B, Ed Robinsons, and Mike Severns are all highly regarded charters that go out of Kihei, with the ride to Molokini being about 15 minutes instead of the hour or so that Lahaina Divers will take.
If you want the boat ride and/or 2 guaranteed dives in Molokini crater (Lahaina Divers always does 2 crater dives where other ops will do one and go back to Maui for an off shore dive), stick with Lahaina Divers. The boat trip to Molokini is gorgeous and the big boats are very comfortable...just be prepared for long.
If you're only doing a couple of shore dives, consider making Black Rock one of them. It's a shallow dive so you can get very long bottom times, but there's oodles of critters to see. On our last Black Rock dive we saw Eagle Rays, Turtles, Nudis, Octopus, cleaner shrimp, just to name a few of the more interesting critters.