Thanks for your question Judy.
I would suggest that your daughter advises the parents that they will be doing a food related activity and asks the parents/carers for a suggestion on what biscuit they are happy for the student to have.
They may be more than happy for him to have what the other kids are having and just adjust his insulin accordingly that day. If so, this is likely to make him feel more like the other kids. If not, they will be able to let you know what biscuits they include in his usual meal plan.
Most of the biscuits that meet our nutrient criteria are the fruit filled biscuits such as Arnott's Snack Right Fruit Slice or Fruit Pillows however depending on the activity, I am not sure how easy these would be to "decorate"!
It is great that your daughter has taken this students needs into consideration when planning her activity.