i have a question about the movie ' I AM LEGEND' ?

i dont understand the concept with all the mannequins in that record
store that will smith goes into and the scene where there's a
mannequin in the middle of the road and he tells him to move or
something and shouts at him cause its dangerous?

and also what happens to will smith's wife and kid after they get in
the helicopter? do they die? if so, how and do they show that scene in
the movie?