I have never seen a stage production of "Oklahoma!", but I own a book, which is called The Theatre Student: Guide to Broadway Musical Theatre (by Tom Tumbusch).
The full description for the stage version of "Oklahoma!" includes the following passage:
"CASTING: 22 parts, 10 principals. Aunt Eller, character woman, sings. Curly and Laurey, romantic leads, legit voices, good acting ability, minor dancing. Will, comic actor who dances well and sings. Jud, character man with rich, deep voice. Ado Annie, comedienne who sings well and dances. Carnes, Cord Elam, Ali Hakim, mostly straight roles with singing. Large separate singing and dancing ensembles. Total cast, 35-50."
The basic plotline of the show is as follows:
The year is about 1900. The tomboyish Laurey is an orphan who lives with her Aunt Eller. Curly is a cowboy who likes Laurey, but he teases her so much that she decides to deliberately spurn him by going to the local box social with her posessive hired hand, Jud Fry.
Jud is the type of guy whom society won't allow into their ultra-clean circle, and he's obsessed with Laurey. She becomes uncomfortable with Jud's behavior, and she pushes him out of the buggy on the way to the social. Jud follows Laurey, and he confronts her roughly, so she fires him.
She and Curley reconcile their disputes, and they decide to marry. After the wedding, Jud appears so that he can take Laurey away from Curley, but Jud falls on his own knife, and he dies. The townspeople decide that Curley isn't to blame for Jud's death, and Jud and Laurey leave to start a new life together.
The subplot of the show, which involves Ado Annie, Will Parker, and Ali Hakim, is fairly adult-themed.
This show isn't exactly a show for children, but I'm wondering if your child might be able to be a part of the chorus.
I know that "The King and I" is one Rodgers and Hammerstein show which revolves very much around the involvement of children. "South Pacific" features two children, and, of course, "The Sound of Music" includes children.
Thanks in advance for your reply.