I would like to recommend Córdoba or Picado for your child. About the guitar's size, you have to bring your child to guitar store/shop to have a look and try...or have an experienced guitar teacher first. S/he will give you better suggestion based on your child's hand size...to keep your child's interest to learn guitar, first nice sound, second easy to play...that means always use smaller guitar.
Otto Vowinkel Concert
German V. Rubio Concert