The horse and buggy tour takes as long as you want because you hire the buggy just for your use. Cuzama is 40 min. away from Merida; Cuzama has 3 cenotes and if you visit them quickly, lets say 20-30 min. each, the tour should take you about 2.5 hrs. All in all you can do the fast version of the tour from Merida in 4.5 hours. I see you want to do Cenotes and Mayan temples in 9 hours, thats a bit too much if you do it on your own. Consider Dzibilchaltun if you want to see the Mayan Temples and an open air cenote, its between Progreso and Merida. Also consider hiring a driver to see if you can get to all the places you want. Drop them an email to make an estimate:
LAWSON: lawson_william@hotmail.com
YUC. CONNECTION: info@yucatan-connection.com