Ambergris Caye really does not have any true all-inclusives, where everything is included, rooms, food, booze, tips, equipment, transfers, etc., in one price.
And a good thing, too, in my opinion. Ambergris Caye thankfully is not Jamaica or Playa del Carmen.
A few places, including Cayo Espanto, Captain Morgan's and Journey's End, do offer packages which include most everything, though not absolutely everything.
Elsewhere in Belize, a few jungle lodges including Chan Chich and Chaa Creek, offer semi-all-inclusive packages. But Mopan River Resort in Benque and the new Kanantik near Hopkins (US$300 a day per person) are the only true all-inclusives.
Belize books and publications by Lan Sluder:
Belize First Magazine http://www.belizefirst.com/
Fodor's Belize and Guatemala Guide
Belize First Guide to Mainland Belize
Adapter Kit: Belize
Fodor's UpClose Central America
Belize Book of Lists 2000
San Pedro Cool (coming soon)