Don't you think launching weapons at a Child multiple times is cheap shotting?
Shin used kid Shin as a Human shield against Sasuke's Fireball. If Sasuke wanted to kill Shin he could easily do so.
Did you notice how he used a Fire Ball jutsu instead of Amaterasu? Sasuke,and Naruto wanted him alive so they could question him.
Also,he couldn't have hit Sasuke with his sword as easily as he did Naruto. Naruto was standing right behind Sasuke thus allowing for an easy hit, in order to hit Sasuke he'd have to do more than simply move his sword backwards.