Of the three specialties you've mentioned (Facial Plastic Surgery, Plastic Surgery, Oral Surgery) you will likely be in good hands as long as the face, and specifically facial implants, are their focus. Seek out a facial implant expert regardless of the board certification.
The experience of the surgeon is more important than what their specialty is. Look for a surgeon who has performed many( over 500) chin implants and has a low complication rate.
You need to be evaluated by a surgeon, the specialty is not important, who is qualified and has extensive experience with complete facial analysis as well as the surgery that is recommended from this analysis. Whether you only need implants or bony surgery will depend on your analysis.