Divibg in Hawaii can be exceptional but some of it is not within cruise parameters. My buddy did a south Kona dive once and was joined by 200 of his firends - Spinner Dolphins. I've dove with Mantas off Maui, Huge Turtles off Kauai and probably 4-5000 Butterly's, Moorish Idols and about a dozen white tip sharks off Lanai. Mot a dive for your wife though, we flew by the fish and could not stop unless we hugged the bottom.
The issue you'll have is that on several islands the boats go out between 6-7am and you likely won't be in port yet. One good thing is several shops do shallower afternoon boat dives - often their cert dives or discover dives but they're still to good dive sites. One I prefered over the meh deeper dives we did that morning. Also they're usually along the coast so shorter rides giving you time to get back for dinner
You dock inn Kahului which is east Maui. All the diving is on the west shore and the boats nearest to you in Kihei (you would need a car) all leave very early from the boat ramp there - plan am hour for the ride over. So that seems difficult.
One option would be to shore dive, those are often in the afternoons. Plus it might just be you and a guide. Some to contact: Maui Dreams Dive Co. in Kihei, Shaka Divers in Kihei, Scuba Mike ot possibly Extended Horizons in Lahaina. There's a lot of decent shore dives from Wailea/Kihei up the coast to Kapalua. Nost are fairly shallow, you have to swim a long way out to hit 60' Sherato Black Rock is an easy shallow dive in Kaanapali, I also like Wailea Beach in Waileas as the good diving along the south side starts around 20'.
Both are nice beaches and backed by resorts for food etc.
Also check with Lahaina Divers - their afternoon dives would be tailored for your wife and are often to one of the generic Turtle Town sites where you'll see some.
Also being on that side of Maui you aren't too far from the Road to Hana which is a nice, scenic, waterfall filled drive. Go with a tour, it's one of the twistiest roads in th US,
Find something else to do from Hilo, it's over an hour drive to diving from there and you'll be in Kona later that week which is where it is. Maybe a Volcanes National Park tour since it's fairly close by. Hilo is more of a locals/port town. There's only one shop, no dive boats and about 2-3 average shore dives you'd have to drive to.
Depending on your arrival time in Kona - should be early asa it's going to take about 2 hr.s. - you should be able to find some dives. Most of the shops have offices in Kona and their boats in a harbor a little north of there - ask about shuttle rides as a few provide them. Try Jacks Diving, Kona Honu, my favorite Kona Diving Co. or Big Island Divers. Jack's is a longish walk from the cruise dock - on South Alii Dr - the waterfront road. The other shops a little inland in a condo mall -- all 3 of them. Take a cab it's easier.
Kauai is really georgeous so you may want to be tourists there. No shops around Nawilwili but Seasport Divers has a shop in Kapaa but their boat is south in Poipu so check if they have a shuttle - Poipu is maybe 30mins drive - and the shops there and boats in two different locations.
Seasports and Fathom Five keep boats in Poipu - actually a harbor nearby. A good dive that should fit into your cruise departure schedule is Sheraton Caverns - interesting open swim-thru's in collapsed lava tubes and lots of big green turtles. Some of the other boat dives might not be good for your wife - Fast Lanes is one to probably avoid.
IDK Oahu diving well enough to comment.
Of course there you've got Pearl Harbor or Waikiki Beach also. The Waikiki Aquarum though small has two interesting exhibits - one is they do critically endangered Monk Seal rehab and you can view them. Also in a small tank in the back we found live Chambered Nauitilus - I have never seen them anywhere else and I've been to many of the best aquariums. They also have some cool outdoor tanks at the entrance.
hth, about the only helpI can offer for Oahu is contact Gabe at Kaimana Divers and see what he can offer. He's on SB as Scotti the Duck