I agree with Jo. The RTD's, bars and soy crisps would be ideal for school because they wouldn't have to mix anything or take packets. So maybe breakfast at home, RTD for mid-morning snack, bar for lunch and then a soy crisps or a sugar-free jello that comes ready made. If they want to have a the lean and green for lunch, you could always prepare that as a home lunch.
From my own dieting experience that started at age 10
, I often felt self consious about mixing up a slim fast shake with my cafeteria milk (in the old days when they didn't have RTD's).
I have a friend whose daughter is thinking about doing MF. If she decides to do it I will make sure to get feedback from her or direct her to this site so she can post comments and get support here.