I like Kona Honu too, but regarding the Crescent Beach shore dive, I've seen Tigers there, but I've never seen any dolphins--not underwater, not even on the surface while between the dives. To see dolphins, you have to go south of Kona, to Honaunau or Hookena.Kona Honu is very good. They have all the specialty dives - small boat long range, black water, Manta etc..all good. (Try to get your wife to do Manta snorkle while you dive. Easy and great IF Mantas are around. Ask first.) I'd mention you're a DM and also maybe join their club for discounts. I routinely get 100cuft Nitrox tanks from them, which I like very much. Just had a great dive with KHD last Wednesday: I also like Kohala Divers for up the coast. Super nice people who love diving. Jack's and Big Island Divers I have also enjoyed in the past.
Btw: there is a very good shore dive right out from Crescent Beach (aka Dog Beach), by Honokohau Harbor, where dolphins and sharks are frequently seen. It's literally a short walk from Kona Honu boat dock. The portion on a lava trail is slightly sketchy - i bring hiking pole for steadiness. Puako has nice beach dives too as does two-step and there's lot's more. September is warm/hot in the air and water and pretty thin on tourists too !! Make sure the operator you want isn't dry-docking then.