Just got back from Belize last week. I would definitely take the Caye Caulker Water Taxi for the day. Perfect with a 4 year old. We loved Caye Caulker!!! When you get there go to "the point". Blocked in area about 2 feet deep for your daughter to play in. Snorkeling and sand bars that you can stand waist deep in the middle of the ocean. Helpful hint...we took a life jacket ($15 at Target) with us in the ports. My 4 year old held my hand while I snorkeled. He went everywhere with me. We just got him used the life jacket before we left. I felt totally comfortable him playing on in the water at all the beaches in the ports.