Tort law works in cases like this. The school will be gone, the ‘guides’ will be bankrupted and probably banned from ever working in a similar role.
Criminal charges seem worth considering, too.
During my tour with a Marine infantry battalion in Vietnam, heat prostration was the most frequent return to duty (RTD) casualty we had. We didn’t have heat stroke because we would stop and treat the casualty properly. (Believe me, the VC and NVA were somehow still around when we started out after them again.) Fortunately, there was plenty of water and shade (the key ingredients required for treatment) available.
Even if he signed a waiver, the fact that he did can’t be used to cancel out basic protections of law. One of these protections is the right to receive emergency assistance when injured or sick. Had the deceased fallen down and broken his ankle, would the guides have insisted that he set it himself and continue with the day’s activity? They denied basic medical assistance (which they were probably well trained to provide) to a person showing signs of a severe medical condition. It really doesn't matter what was causing it. Heat stroke is not some imaginary disease arising out of a lack of willpower. Once he had medically diagnosable symptoms, a duty to assist was created. If they claim they weren't qualified or able, the school and the instructors were criminally and civilly liable for the hazard they created for their students and failed to protect them against.
The sheriff needs to talk to the county prosecutor on this one. (Or talk to him again.) I hope the parents’ attorney talks to state attorney general just to ensure favoritism isn’t being displayed by the county towards the school.
I think you are right about the ultimate outcome. They (and their insurance company) will probably lose their a**es on this one and deservedly so. Whether or not they will serve time, I don't know.