Victoria House and Lamanai Outpost are always good choices.
Not to throw cold water on your third choice, but ... I was at Coco Plum Caye last summer, but since then it has changed management -- at the time it was managed by Jaguar Reef. I haven't heard much about it since the change. There is not much snorkeling from the shore there, the island is not on the reef, and the sandflies were pretty bad. However, the cabins do have A/C.
I probably would want to at least look at the some other options, such as, perhaps, Pelican Beach at South Water Caye, or Caye Chapel Island Resort (an unexpectedly romantic setting, especially if there is a full moon -- you can drive around the island in your own golf cart and virtually have the entire island and golf course to yourself) or Isla Marisol at Glover's Atoll.