Free Children’s lift ticket is restricted to maximum occupancy in selected property type. Children must be accompanied by at least one adult in Keystone rental properties. Standard occupancy restrictions vary by property type. Proof of age is required for the Kids Ski Free program of all 11 and 12-year-olds. KSF tickets are valid at Keystone only and are not interchangeable at any other resorts. Children 4 and under always ski free.