Hi Rambo2,
Some stuff about shore diving in general, and shore diving on the Big Island in particular:
1.) Shore diving is wonderful!!! I've been shore diving here since the 1970's. I shore dive exclusively here on the Big Island.
2.) Shore diving gives you 100% freedom to dive on your own schedule, and dive where you want to dive... however, that freedom comes with a price tag: You need to be your own "Dive Master". You need to be able assess the dive site, recognize whether the ocean conditions will permit a safe dive, and be able to plan and execute a safe dive on your own. Navigation ability is a must, and ability to monitor (and plan!) your air use is critical. Otherwise you could be in for a long surface swim, and there can be surface current that makes this a challenge in some spots.
3.) Hawaii shore diving: Is awesome, and generally the conditions are fairly benign on the Kona side, and just about anywhere you can safely enter the water will be a great dive spot. But you do need to be able to navigate back to your entry/exit point accurately since in some areas there may only be one safe spot to enter and exit the water due to lava and shallow reef. Even in clear water, you should be referring to your compass along with "natural" navigation techniques in order ensure you do not get "lost"..... it is easy to get distracted by the pretty fish, and all of a sudden one coral head begins to look a lot like all the rest... and you cannot remember which way the exit was.
Getting additional training is a great idea, especially if you think your basic OW class was a "diploma mill".
Jack's Diving Locker did a great job with my 3 kids' AOW training several years ago, and I've also heard good things about the other dive ops in Kona. I'd recommend calling or e-mailing several of them, and choose the one that is the best "fit" for what you are trying to achieve.
If you feel like you need a little extra one-on-one time with an instructor prior to beginning AOW (which may be a good idea), you might want to arrange that as part of your AOW course. I imagine any of the instructors with the Kona dive ops could spend a little time with you and greatly improve your "basic" skills and help your confidence immensely prior to beginning AOW.
Have fun with whatever path you choose! Shore diving is the best!
Best wishes.