Philippians 2:14 ~Do everything without whining, complaining or arguing. ~ Every one has their own jar. Start off the week with a set amount of quarters in each jar. If they are caught whining or complaining, they lose a quarter and their sibling gets it. (Ouch) If they argue, they each lose one and mom gets them. At the end of the week, they get the money that's left or you could put it towards an activity.
Kids want allowance? You could have these each week and when each one is done they go in a jar. Then, at the end of the week put them all up again.