The description in established E/M codes states "physicians typically spend X minutes face to face with the patient and/or family". This statement leads one to believe that a visit with the mother would be billable. However, it is probably best to check with the payer; as the previous replier stated, it probably isn't Medicare.
We did have one instance here in my clinic where the parents came in; we were told by the payer prior to the visit (it was Humana, if I'm remembering right) that the claim would be paid. We were doubtful, but the insurance did pay it. So it is possible.
Hope this helps!