This scene shows the sacrifice aspect in The Lottery. It shows that citizens in the town are sacrificing Terrie for the ritual, the tradition, and the harvest.
The children getting the rocks ready and gather together foreshadows that they were going to use them for something in the Lottery. They eventually used it on Terrie.
When the Lottery is just getting started and the names were being he pulled the mood was very ominous and a little too clam. In the text it states, "She held her breath while her husband went forward." This means that when the woman's husband went up she got nervous and held her breath.