This is something that you should answer for yourself because your feelings may well be different from mine. I will explain my feelings.
To me, what the three greasers did for the kids who were trapped in the fire is rather heroic. I feel that it is heroic because they put themselves in a very perilous situation when many other people would not have done the same. I would imagine that the majority of young teens, when faced with a similar situation, would feel that they were unable to be of help. They might want to help the kids in the church, but they might figure that they were unable to help or they might feel too afraid to try.
I am saddened by the fact that Johnny is so badly injured and I fear for his life as well.
I agree with previous post that the boys' actions were quite heroic when they entered the burning church to save the children. I believe they also acted out of a feeling of guilt, since Johnny and Ponyboy caused the fire and put the children's lives in jeopardy when they left their smoldering cigarettes in the church. Johnny, who led the charge into the church, had a poor feeling of self-worth, and he may have felt that the young children's lives were more important than his own. It was gratifying to see Dallas risk his own life, albeit to save Johnny and Pony rather than the kids inside. And it was sad that Johnny, the book's most sympathetic character and whose life had more obstacles than any of the others', had to be the one to die.
I believe Ponyboy, and Johnny may have felt themselves responsible for the fire, which is most likely the reason they were so quick to rush to the children's aid, despite that I believe Pony and Johnny would have "risked their necks" for the children any way because both of them I believe feel they have some sort of moral responsibility to do so especially since they are quite capable youths. As for Dallas he would not have gone to help if not for Pony and Johnny he would have done all he could to avoid that situation. Not to make him sound heartless but, Dallas only cares about what he knows and everything else he couldn't careless about. From "hoods" to heroes as said before heroic.
They risked their own lifes to save all the childrens lifes but from doing so johnny got injured