If they are going to San Pedro, then we have a Salar de Uyuni leg for sure!
I went there last summer, and the town of san pedro is empty, there is nothing to do there except some sandboarding, and biking. But it's the closest town to the Salar, wich is an amaing thing to see! And it's really easy to cross the boarder + even if there are some tourist that may see, they can report for a good 3 days because there is no wifi in the desert!