For a special destination, since it is so hot here in south Louisiana in August, I would head to Alaska for a “special” trip, probably the Bristol Bay region? For a more expensive experience, perhaps Bristol Bay Lodge, or for more reasonable prices with more for the non-angler something close to Katmai Nat’l Park like Brooks Lodge. But that’s me.
For warm & salty, I might focus on a central-american destination where he had a good chance at a grand slam, Turneffe Flats (Belize) comes to mind, also might try Roatan (Honduras). I think Belize would have a lot more for his wife to do.
There are other cool places to go, but (1) I don’t think August is the time for an Angler to go to some of those places (Argentina, New Zealand, Costa Rica), or (2) others are not friendly to the non-angler (Russia, Labrador).
Seychelles does sound intriguing . . .