People often think that the purpose of a children's choir is to perform during worship from time to time. Performance (or celebration) is the goal, the frosting on the cake, but the real heart of a children's choir is in the week-to-week community-building and skill development that occurs.
A simple model of a children's choir is to rehearse a song with a group of children. Rehearse it four or five weeks in a row (or more, if you have children who attend on alternate weeks). Have the group memorize the song, and discuss what the words mean, telling the song's stories. Then have the children share the song with other children or with the entire congregation.
For this simple model, I recommend that the children in each choir be within the same age range. Quite often older singers don't want to sing with younger singers. They don't want to sing "children's music"; they want to be challenged. For special occasions it is possible to mix older singers and younger singers, but I recommend that the youth be assigned as big brother/sisters for the younger children. Assign them actual responsibilities, not token jobs.
More advanced children's choir models require one or more professional conductors and several willing parent volunteers to coordinate the numerous details involved. Ideally, this model encompasses three age groups roughly divided by grade levels (grades 2—5, 6—8, and 9—12) or by level of singing ability. Many larger churches, such as the All Souls Unitarian Universalist Church in Tulsa, Oklahoma, and The First Church in Belmont, Unitarian Universalist in Belmont, Massachusetts, have ambitious children's choir programs.
The Unitarian Universalist Musicians Network (UUMN) publishes a guidebook on staffing a music program, called Music In Our Congregations: A Handbook for Staffing a Music Program in UU Congregations (see Resources). The UUMN also sponsors the National Honors Children's Choir that coincides with the UU General Assembly. Contact the UUMN at firstname.lastname@example.org for information about auditioning children from your church for participation.
Whether you choose a simple or advanced model, I recommend that your choir(s) be repertoire-based, which simply means that you feature several songs in a repertoire for years at a time. These may even become theme songs. The more the children share the songs with others—for example, during worship or coffee hour, at church potlucks, at other places of worship, church bazaars, or on civic public occasions—the better they will become at singing and the stronger their community will be. Encourage the choirs to move their bodies, whether by swaying or engaging simple hand movements, to better bring out the message of the song. More adventurous choreography is not beyond the reach of most children. Certainly circle and line dances can work beautifully. There are few things more beautiful than a children's choir singing a processional or recessional. Dim the lights at night, light candles, and you have something that is downright holy.
Three incentives that will attract members to your children's choir are children's musicals/operettas, choir tours, and camp retreats. All require a lot of parent volunteer time, but they also do wonders for retaining singers in the choir program.
The great singing congregations are the ones in which the music director sees the congregation itself as the primary choir, with smaller choirs and ensembles within it. Similarly, you can treat your entire children's and youth program like one giant choir, with smaller sub-choirs organized by grade levels. Remember what songwriter Bill Staines has sung many times: "All God's critters got a place in the choir." Such a goal requires tremendous vision, but that is what Tapestry of Faith is all about: tools to make our faith communities come to life.