If money is absolutely no object, I'd say Cayo Espanto, a small four-villa resort on a postage-stamp size island just back of Ambergris Caye, is the # 1 honeymoon spot on or near the island. You have your own butler and meals are brought to your villa, where you can lounge on Egyptian cotton sheets with the walls folded back, just steps from your own private splash pool.
Second best for a private honeymoon on Ambergris Caye is probably Mata Chica up on the north end of the island. Stylish thatch cabanas and new villas, with a good restaurant. No pool, though.
If you want to be fairly near town, I'd recommend one of the following: Villas at Banyan Bay (2-bedroom units are very nice and have jacuzzis), Victoria House or Banana Beach. All of these are 1 1/2 to 2 miles south of town.
Golf carts are priced about like a rental car in the U.S. -- US$60 for 24-hour day.
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