I still think a high scoring candidate for why they left their tent is the military test of a low yield tactical nuclear device. These weapons were designed to minimise physical damage ( albeit it is still a very big explosion) equivalent of several kilotons. An air burst of such a device at even a couple of km from their camp site should have the desired effect. They would be hit with a heat flash that would not have burned them but could possibly cause blindness if stared at directly. The blast would knock them around in the tent like someone shaking a bag of wall nuts but would not been sufficient to kill them. The wind blast would buffet the tent and be enough to throw anyone standing up outside. The shock wave would likely be sufficient to cause permanent damage to ear drums and hearing. And they may have been exposed to a significant if not lethal dose of neutron radiation. At extreme high levels the radiation could have an immediate effect on them, including their nervous systems, causing confusion, disorientation etc.
If after the heat, flash, blast and wind blast they emerged from their tent, they would have seen a huge fireball in the sky. This may have been enough to cause them to panick and flee from the camp site.
It is at this time in history that the west were developing these weapons. Between 1958 and 1961. It is likely that the russians were also experimenting with these weapons.
Evidence to look for would include a large area of melted ice directly below the detonation point. The ice may have melted and then froze again forming an icy crust underneath any snow that fallen after the event.
Fallout from the device would remain highly radioactive for about 2 weeks after which it would be safer to reoccupy the area. Even so depending on fallout plume dispersion, there would still be evidence today if the right core samples were taken and analysed.
There is is circumstantial evidence that different groups of people, some 70km away witnessed orange orbs in the sky in the direction of the pass that night. Also Ivanovo later said that he noticed that some of the trees had scorch marks on the tops.
In terms of the victims if they had been exposed to high levels of radiation, the symptoms would include the rapid deterioration of the stomach lining, intestines as well as the immune system leading to rapid and serious infections of the blood. This could have killed within 2 days to a few weeks. The cold was even a bigger threat that night so this would have killed them before any radiation sickness.
The government would certainly not want any probing investigation that may lead to the development of their new technology, or that any tests caused the deaths of these kids. It would be a good reason to cover it up and shut it down, and ban access to the area to stop people being exposed to any radioactive fallout.
It's also interesting that although the radiation found on the cloths of some of the victims was only minor, that the helicopter pilots refused to take some of the bodies onto the helicopters and said that they wouldn't unless they were in zinc coffins. Is it possible they knew something the investigators didn't?