I second Lan's opinion about Pook's Hill. We stayed there last week for 4 nights with our 7 and 10 year old. It was very nice, and the kids had a great time. The owners, Ray and Vicky Snaddon, were extremely gracious and helpful. One thing to consider - everything (with the exception of horseback riding) you do on the property is free. You can go river tubing, swimming in the river, take guided jungle hikes, explore the Mayan ruins.
I thought the cabanas were very nice, and the grounds were beautiful.