The traditional practice is to light two candles on Shabbat. One symbolizes the idea of remembering the Sabbath, "remember the Sabbath day" (Exodus 20:8), and the other symbolizes observing the Sabbath, "observe the Sabbath day" (Deuteronomy 5:12). Some families light more than two candles. They may light one candle for each child or for each member of the family.
For small children, it can be a treat to blow out the match used for lighting the candles. Whether one lights two or several candles, their glow makes the Shabbat dinner table even more special.