In a sense, the children only create their games as a result of the prejudices that exist in adult society. For example, the children only create the Boo Radley "games" because of the rumours and urban legends that already surround Boo Radley. In a sense, all they are doing is trying to make sense of them themselves and to understand them and the complicated world of being an adult in this environment. Note how Boo Radley is referred to in the opening chapter, where the reader first hears about him:
Inside the house lived a malevolent phantom. People said he existed but Jem and I had never seen him. People said he went out at night when the moon was high, and peeped in windows. When people's azaleas froze in a cold snap, it was because he breathed on them.
Boo Radley is referred to as others as a bogeyman, a universal evil who is responsible for all wrong in the world of Maycomb. Note the metaphor which compares Boo to a "malevolent phantom." It is no wonder, therefore, that the children hit upon the idea of playing their games in order to help them make sense of what is going on and why it is that Boo Radley is such a fearsome figure. Society has dehumanised him, and so the children follow suit. They are not to be blamed, because they are only responding quite naturally to the prejudice that there already is in their society.