It’s best to set up an appointment with the person in charge of catering at your child’s school to discuss your child’s requirements and to air any issues which you may be concerned with such as cross contamination.
Most schools now cater for a large range of allergies and intolerances so it should not be too difficult for them to provide gluten-free food. Give the school as much notice as possible and put your request in writing. There is a sample letter available from Coeliac UK which you can tailor to your specific requirements.
It is worth mentioning to the catering staff that you would prefer your child to be offered a similar gluten-free alternative. This will help make your child feel included.
Bring along some easy to follow recipes and offer these to the catering staff. Often people are more receptive once they know what gluten-free means and they have a good idea of what your child can eat. Be very clear about what they can’t eat and give them a comprehensive list of items which they must not give your child. I would also give them contact numbers for Coeliac UK and any other websites which will help them get a better understanding of Coeliac’s disease.