The trip to Ni'ihau sounds amazing. I was in Kaua'i last September and didn't go because tales of the channel crossing on the way back made it sound like a couple of hours of seasick agony. That being said, if I'd been there earlier in the summer I might have gone anyway...a friend went and said it was the best dive EVER particularly Vertical Awareness. I love deep dives, so I was bummed after she got back and said the channel crossing wasn't "that bad" but apparently it's the luck of the draw (keep in mind that she doesn't get seasick. Ever). I HAVE done the Molokini back wall dive with her several days before her Ni'ihau experience. I thought it was unbelievable...she said Ni'ihau dives (the first two, she thought the third dive was just average) beat the back wall hands down (she was especially enamoured by a monk seal, and she said the vis was unsurpassed). She too went with Seasport because of the fact that their boats seemed better equipped for the crossing than Fathom Five. I went on a morning dive with Seasport, they did a fine job. In summation, I'd say go unless you are bothered by violent seasickness. She said it was worth every penny. Btw, the manta ray dive on the Big Island is a MUST DO. Your wife will love the snorkeling--my SO (who can't dive because of ear problems) adored it as well. It's a great trip for diving/non diving partners, both will have a blast. Have fun!