In this case, you write to ask whether it is all right that the item you have or have prepared is slightly different from the one specified by the school. It might be better to ask the teacher directly so that you can show her the actual object. Adding how your child is looking forward to the activity gives the impression of your cooperative attitude towards school activities.
Conversational flow and useful expressions
Whether it is all right or not
You and your child’s attitude or feeling
Attaching "~chan" to a girl's name or "~kun" to a boy's name is usually only done when addressing or referring to children besides your own. It is not very common to attach "~chan" or "~kun" to your own child's name, especially in public.