If you want to do peds exclusively, all of the peds programs I know of have their own, pediatric only internship year. Intern year used to be like MS3-rotating through most of the specialties, but now it is usually specialty specific (transitional years excepted, and I don't think they do any peds-you can do a peds transitional year though, if you were interested in peds anesthesia for instance, but that's all peds).