You have always been able to set a time period fee for an individual registrant, but now you can set a time period fee for a family.
From the left nav panel, select find | time periods and edit the time period you want to add the family time period fee to.
Type the registration fee in the Registration Fee for this Time Period text box and select the Family Time Period Fee checkbox. Save as you normally would.
The first time a member of a family enrolls in something assigned to this time period, ASAP will charge the designated time period fee. If any other member of the family enrolls in a class in that time period at the same time/on the same/initial invoice, or any time in the future for anything in that time period, the family will not be charged an additional time period fee.