Hi there. I was in Maui for the first time in Nov/Dec. Like you, we thought we'd supplement our boat diving with shore diving, not only to save dollars, but for the variety as well. After all, most of our diving around here in BC is shore diving.
We bought a book with local shore dives when we got there, as well as using the Maui dive guide. It was very helpful for locating the sites, as they really aren't marked as such. A lot of areas are great for snorkeling, but too shallow to dive, at least without a huge surface swim out. If you can get a guide, especially for the first dives, it would be well worth it. We were recommended to Shaka Doug as well, as he knows the Kihei/Makena area in particular inside out. We didn't get a chance to dive with him though. In fact, by the time we were going to dive that area the surf and swells were picking up making entry rather difficult/dangerous. We had to lay on the beach instead (so terrible
Again, this is where the locals can help out. Sometimes when it's rough at one end of the island it can be much calmer at the other end, or at particular sites. The seasons can make a difference too. I think you'll have better luck in July.
I did some dives with Tim before my boyfriend got there, and if you get the chance, definitely do dive with him. If he's busy, at least pick his brain about where to dive, especially in the Lahaina area. He has great knowledge of the area and we did some terrific dives. One nice easy little dive to do is Airport Beach. It has handy parking, facilities, and easy entry off a popular beach. It drops to about 20 feet quickly over the reef without a long surface swim. It is shallow, and you'll have snorkelers over you, but for such a convenient site, there was lots to see, including tons of fish, eels and turtles. I went back again with my boyfriend and again saw many turtles and eels. Oh, another thing... it tends to be best to get out there early!
If you do at least 2 boat dive trips, do dive Molokini and the cathedrals at Lanai. Both trips are well worth the money. There's so much to see and the viz. tends to be better further from shore.
Have a great trip!