I would not choose Ambergris Caye. My wife and I have made 10 trips there in the past 5 years (every beginning of December and middle of February). We are not going there any more due to it's increased population and crime. We feel it is no longer safe for my wife to walk the beach. We have viewed, as in toured, practically every hotel/mini resort on the island. Someone mentioned Victoria House. Aside from a couple of spots North on the island which might come close, Victoria House wins hands down on AC. While I can do absolutely nothing with the best of them, Caye Caulker would be a challenge...and next to nill in the way of beach walking...and no descent accommodation. Having said all that, I would choose Placencia or one of several inland retreats such as Coppula's or Chan Chich...or another country.
Safe travels.