I gotta question for those taking care of Oahu visitors: Is there any call for South Shore shore diving? Thinking of Lanai Lookout and Blowhole and the adventurous dives like that. Would you feel comfortable taking tourists on dives like those?
I decidedly don't take tourists or beginners with me for a few reasons, the first being that I tend to dive more "adventurous" spots. I think you'd be hard pressed to find somebody who will take beginners shore diving on the south shore of Oahu.
Lanai Lookout has become a staple of my shore diving, but due to long hikes up and down rock walls, cliff-jump entries and washing machine entries (and that's on a good day) I wouldn't recommend it for anybody who is unsure of their abilities in the water.
Blowhole is a somewhat different story. The walk down is still a little rough, but a little better worn due to the popularity of From Here to Eternity Beach goers. The entry is a beach entry. The dive itself can have a touch of current from time to time, but I've never seen it. The problem with Blowhole is that, like Lanai Lookout, it faces a direction that often takes a lot of swell.
I'll mention a couple more south shore sites you missed. Portlock has become my go-to site when the waves are up everywhere simply because it is the only spot I can readily think of that is easier with a little surf. However, like Lanai Lookout, Portlock should only be attempted by experienced divers. It has caves, wildly varying vis (depends 100% on the tide) and ripping currents that either carry you calmly to your exit or whisk you away into the open sea.
Finally, in spite of its use, Hanauma Bay is spectacular and usually diveable due to its protected nature, but to get to the really good spots, you have to work a little first. Most consider it a beginner dive because it has showers, lifeguards, and easy beach access. I hate beach access and find sand is both a PITA to walk through and a PITA to rinse out of your gear. Also, the wave activity and tides combine to create pretty good out-flushing currents at the channels leading out of the inner reef. Of course, unlike the other spots listed here, you could always wave at a lifeguard and they'll come out to assist you.