This depends on each of your family member's needs. For young kids, I would suggest cutting the recipe in half and using the short cup. If you are using them as meal replacements, then I would use the tall cup and ensure there is plenty of protein and healthy fats as part of the Blast recipe. If you're simply making them as a snack you can make one in the largest cup and split it between family members. It all depends on your needs and the other foods you are eating throughout the day.