Dear Kerry Milis Parker,
Thanks for contacting Top China Travel!
It would take a minimum stay fo 3 days/2nights in Dunhuang to see Magao Grottos, Singing Sand Dune, Crescent Spring, including the arrival date and departure date. Usually, it takes a full day to see Magao Grottos, Singing Sand Dune, Crescent Spring. And you need one day for arrival and one day for departure.
Any further request or question, please feel free to contact with us.