Child of 14 or older generally liable, a claim against the child is possible.
From the age of 14 a minor is generally capable of tort liability if they had the necessary capacity of understanding. They are then liable under sections 1293 et seq ABGB like an adult for a breach of the FIS rules. In practice the family liability insurance, which often includes co-insured children, frequently steps in.
Next steps: secure evidence, check the family insurance cover and pursue the claim against the person capable of tort liability.