Here is another place in favor of a noble cause and encountering phenomenal success. You'll need to book 2 or 3 months in advance and it's often filled-up the rest of the year. You'll find a planning calendar on the main website, while the Little Darwin (P'tit Darwin) section has invitations, descriptions of horse-back riding courses run throughout the year (HappyActivities) and camps (HappyCamper). 

In addition to learning how to ride like a cow-boy or cow-girl, it's also possible to rent out "The Saloon" (restaurant) or sleep outdoors in tipis. Just fabulous, isn't it? Of course, book well ahead... and check out the booking calendar below (link)