Cast six families of 4, make them think it's the same format as TAR8. But then at the Starting Line, shock the families by forcing them to split up into teams of 2, a total of 12 teams.
But during the Race, use voting U-Turns or Intersections and Double Battles/Face Offs to try and break up possible family alliances that may form and to ensure that final 4 or 3 are all different families. It'll be bad if two of the final 3 spots are one family, worse if the final 4 are only two families, you know? lol