Wait just want to make sure I understand Instructor is considering quiting and still doesn’t want to do it. Resort is not talking to instructor and not acting in a responsible fashion.Except that this would create a customer service nightmare for the resort and potentially a loss of job.
@JaneB I agree with @markojp at this point. It would probably be good to talk to your manager within the school to understand their expectations in the situation. Is it possible that this ticket office person booked it and your manager hasn't registered the age of the child?
Take initiative and be responsible to your ethics, if you have too. No matter the outcome, customer safety first regardless of what the boss wants. No job is better than lawsuit for negligence taking the blame for a firm that will string you out to dry.