Circunstances are different in every case and fighting may have been the best course of action for your group. It didn't sound like the kids that were attacking you had the gun against the back of the head. I don't blame these kids for not fighting back. There were only two of them at a time against a criminal with a gun.
I hope the girls are not dead. The fact that he didn't kill the young men leads me to be hopeful for the girls. If the young man had fought the guy, he would be dead. Against a gun at the back of the head, this young man had no choice.
I fought a mugger once. I was so mad, he took all the money I had, he kept hitting me and hitting me in the back of the head. He finally stopped and I was still mad, I thought about running after him. At least my common sense finally took over. I let my adrenaline take over and was stupid to have fought this man even though he didn't have a gun. Being a woman, I didn't really have a chance against him. I wouldn't have been hit repeatedly if I had just let him take my purse.
These young men were doing what most of us would have done with a gun butted up to the back of our head. The one young man said he thought the man had only planned to rob them.