It is possible that the only thing that would result from the thinking of those who are stating that if only the woman with the young child had been carrying a gun is more Trayvon Martin like shootings. In the case of the mother with the young child a gun might not have changed the results for the better. According to her story, the young men walked up to her and either asked for or demanded money. When she said she did not have any money she was shot in the leg and the ear. Next, her son was shot in the head. If the woman had been carrying a gun it is likely she would have had to reach for the gun in some way. The moment she reached for the gun the young men most likely would have shot her and then shot her son. So, the results likely would have been just about the same if this woman had been carrying a gun.
Considering the way things happened with this woman and her child the only way she would have been safe was to shoot the young men the moment they said hello, or the moment they got too close. As a result, you end up with more Trayvon Martin like shootings. Since you cannot wait to see if the person is a threat you just shoot the person because you think they are a threat. What happens if the person you shot turns out to not be a threat? Oh well, you were trying to protect yourself and you did not want to take a chance that the person was not a threat.