I would glady use the paid service of MileageManager if they had some sort of family plan. I'm the primary mileage/points collector but my wife and 3 children also keep a few small balances which I track for the family. Because of how MileageManager is priced, this would cost me $75.00 per year ($15.00 X 5).

I can track all of them with one logon for free from MileTracker which comes as a stand-alone product for free from USA Today.