The production originally was scheduled to close Oct. 5, but is now slated through Oct. 19.
The musical is based on the "Little House" books of Laura Ingalls Wilder. Gilbert, who played the title character on the television series, takes the stage as Caroline Ingalls - perhaps better known as Karen Grassle's "Ma."
The added tickets range from $34 to $65 and go on sale Friday. Opening night is August 15.