Will they fly more in the near future? Are they looking to earn status or would they just like to earn miles they could use for free travels?
If they are looking for status I would recommend AC Aeroplan, only 35000 needed for Star Gold. This trip in SQ J will earn a bit more then 25000 miles which means only 10000 away from Star Gold.
Since they are based in Norway I would also like to recommend SAS EuroBonus. With this trip they will earn more then 40.0000 EuroBonus points(became Star Silver). Note that only 12.000 is needed for travels within Scandinavia with KF,SK,WF and BU.