Hi MrsBoyle,
carb counting is where you take the carb content of a meal eg 40g and inject the correct ratio of units for yourself (everyones different) ie 1unit per 10g carbs = 4units of bolus (ie humalog, novorapid) this would be along with a basal (background insulin) like Levemir or Lantus.
Hospitals usually put children onto a premixed insulin to begin with when 1st diagnosed like mixtard 15/25/30 ect. and eventually they progress onto 1 basal and 3 bolus insulins a day, and thats when the carb counting comes in and is of great value in controlling their diabetes and is much more flexible.
But then again knowing the carb content and how they work can also be of advantage in keeping numbers correct when on a premixed insulin, but then again the child is still in the honeymoon period and it can all get so confusing. Until your child is put onto a basal/bolus regime, i would just get familiar with looking at food labelling and working out the carbs, so that your ready for the change over. Your hospital will send you on a carb counting course prior/during the changeover and it's always good to be prepared.
Hope this helps,
Suzi x