This is a really sad story. I totally feel for the family. The pictures in the article show that he was a scout leader. The older of the two boys was a Wolf cub scout. That makes him about 8 years old. The younger brother is probably 6 years old. I have kids that old and it is VERY easy to understand some of the challenges he would be up against. When young kids get wet and really cold, they won't move anywhere. He likely carried one or both of them a long way trying to make it to a safe location. I sure the kids literally shut down long before he did. In that state, there is little to no chance they can contribute to making a shelter and he likely doesn't want to distance himself much from them to gather what he needs to provide some sort of shelter. There is no way he is going to leave them out there to make a fast trip for more help either. He probably carried them until he didn't have the strength to continue, then the three of them cuddle together under a large pine to try and stay warm enough to survive the night. But being soaked to the bone and temperatures in the 20's, hypothermia takes 3 lives.
We would hope that ponchos and emergency blankets would have been enough to keep them alive. I've slept in emergency bivvys and done survival overnighters, stayed overnight on hunting trips in a AMK bivvy because no sleeping bag was available. Emergency blankets suck. IF emergency ponchos would have kept their body cores dry and they could have had the emergency blankets with their body warmth together, I agree they likely would have survived the situation.
Sad, sad, sad...