The cabin we stayed in was exactly as described. It had an optional air-conditioner, but we never felt the need to use it (First week of October). We wanted something simple and modest since we would be out exploring every day. The campground itself is more beautiful than the pictures. If feels so secluded, but you are very close to everything in town....within walking distance.
As far as hosts go, Francisco was the best! He gave us excellent recommendations on where to eat and things we needed to see while in the area. He even set up our trip to Tikal. My advice would be to take his recommendations without any questions asked :). We will definitely stay at Mana Kai If we are able to get back to San Ignacio in the future!