The one responsible for doing much of the direct work with scheduling would be the receptionist. Account executive would be responsible for the insurance and billing, while the dental hygienist and assistant are responsible not for such paperwork, but can tell the receptionist the next course of action.
A 12 year old male should have a caloric intake between 1800-2400 calories per day. Thus, your percentage would be based on that days specific caloric intake.
Using 2000 as a average, the 900 calorie burger would be 45% of your daily calories.