Penalty notice for unauthorised holidays

This is my first post please be kind my punctuation and spelling is not great

My husband and I have just received penalty notices for my 12 year old ASD son as we took him on holiday during term time my son can not deal with crowded places and lots of over excited children we obviously want our son to experience every opportunity we can give him but find if we take him away during school holidays it is too stressful and overwhelming for him so we have no choice but to take him during school term time when it is quieter and he can enjoy his break away. My son is in mainstream school and the school are well aware of why we take him away during term time. Has anyone else had this issue and is there anything we can do about the penalty notice as it states we have no statutory right to appeal but feel there is exceptional circumstances for the leave