When to go
December through May is generally the drier window, but reef departures, cave access, small-aircraft flights, and sargassum can change week by week. I keep the key water day movable and reconfirm marine conditions close to travel rather than pretending a seasonal average can promise a perfect beach.
Hotel logic
The hotel should solve the base. Blancaneaux Lodge, Gaia Riverlodge, Chaa Creek, and Ka'ana make Cayo feel deliberate. Matachica and Victoria House suit different versions of Ambergris Caye. Hamanasi links reef and rainforest from Hopkins, while Turtle Inn, Naia, and Itz'ana make Placencia a stronger coast-and-village base. Cayo Espanto and Royal Belize are privacy plays, not substitutes for seeing the country.
Food and reservations
Belizean food changes with the route. San Ignacio is useful for inland Belizean cooking, Hopkins for Garifuna dishes such as hudut and sere, Placencia for Creole cooking and seafood, and San Pedro for the widest restaurant choice. I would rather build around culture, the day's catch, and seafood seasons than default to the most expensive resort dining room.
What I would avoid
I would not sell the Great Blue Hole as mandatory, promise a Maldives-style beach, or squeeze Cayo, multiple cayes, Hopkins, and Placencia into one week. The scenic flight often explains the Blue Hole better for non-divers, while Hol Chan, Turneffe, Glover's Reef, or Lighthouse Reef shallows can deliver the richer marine-life day.