I believe if I were you, I would specifically ask his doctors why they feel this insulin is the best. There are many insulin possibilities, and I believe that the best treatment is to find the one that works for each individual the best. Without trying something different, you can't know if this is the best for him. Is he seeing a pediatric endocrinologist? If not, I would request a referral. Blood sugar spikes and drops are going to happen on occasion but don't have to be the norm. It sounds as if the mix is not matching his digestion times comfortably, and you don't have to live with this problem. A good endocrinologist will keep adjusting insulins until the blood sugar levels stabilize most of the time. Other options include both pumps (yes, for kids as young as 10 years old) or injections of long-lasting insulins like Lantus to provide a stable rate of ongoing insulin delivery (different for each person) plus either Novolog or Humalog at meals to cover the meals only. It sounds as if the mix is not doing the job properly for your son -- nowadays, you shouldn't have to keep forcing food to catch up with insulin nor should he have to live with high glucose levels several times a day. Better options exist, and I would encourage you to insist that they be explored.
I totally agree with the Vol. No need for this and my first reation was why a mix !?!?!?!?!? Mixes are easy but can have this effect quite often especially as it seems his schedule is somewhat irradic. IE. more exercise and less food in the afternoons and visa versa in the mornings. If your Dr. is not an endocrinologist you need one and if he/she is and is unwilling to consider other insulins then you need a new Dr.