The experiences were private and high quality in my opinion. We took a horse ride through the desert which was the highlight of the trip for me. We went diving in the hot springs, visited the Chaxa Lagoon, the Moon Valley and had a star gazing lesson. We didn't have time to visit the Tatio Geyser though that was an option. Higher altitude activities are taken nearer the end so that you have acclimatised. I wrote a blog post about the activities in detail with pictures:

Eight Things To Do in the Atacama Desert - SilverSpoon London