If you are newly certified, you might consider doing some shore-based dives for your first day.  Down near Kihei there is Shaka Doug, and up near Ka'anapali there is Tim from Tiny Bubbles scuba.  Both get great reviews (I've dived with Tim, and was very happy with the experience).  Stepping off of a boat in deep water the first time can be a bit unnerving for some people, whereas wading in from shore is more familiar.

Since I stayed in the Ka'anapali area, I did a bunch of boat dives with Extended Horizons who do much of their diving off of the island of Lanai.  I also did a trip with Ed Robinson out to Molokini, which was really cool.  I was happy with both of these operators.

Have fun!