Although I cannot diagnose a patient with seeing him/her, in general at age 12 expansion can be accomplished with a non-surgical approach. Another factor to consider is the severity of the problem and how much expansion is required. If a child of 12 has a disproportionately large lower jaw sometimes a trial non-surgical approach is recommended. Lower jaw growth usually continues until the bodily growth is complete. So if the patient has surgery at 12 years of age, he/she could outgrow his/her treatment.
Talk to the orthodontist about your concerns. If you still don?t feel comfortable with his/her advice, get a second opinion.