Can a chin implant make for a slimmer face?

You need to submit  couple of good photos before you can expect to  get any sort of useful recommendation.

Hi, I have performed many facial shaping procedures using dermal fillers, facial implants (cheek, chin), liposuction and/or facelifts for over 30 years.  Non smiling photos of your face from the front and side would help in the evaluation. 
 Following my the facial beauty principles that I've developed over the past 30 years I have found that women look the most feminine, youthful and attractive with heart shaped faces.  Heart shaped faces have cheeks that are full and round in the front.  Cheek augmentation with a dermal filler or using cheek implants for a permanent enhancement will create full, round cheeks that will feminize the entire face.  If your face is round, oval or rectangular, cheek augmentation can create the more feminine heart shaped face.  If excess fat exists in the face and or neck, liposuction would be combined to further shape the cheeks, face and neck.
 If your profile appears out of balance, it could certainly be due to a weak chin.  I have performed many Chin Augmentations using chin implants for over 30 years and have found that a weak chin creates an imbalance making the nose appear larger, the mid face top heavy and the lower face look short that de-emphasizes the lips and allows early formation of a double chin.  Chin augmentation using a silastic chin implant will add projection to the chin creating harmony and balance to the lower face. 
 I place the silastic chin implant, through a small curved incision under the chin (also allows excess skin removal) to be very safe, quick, highly effective and far less invasive than a sliding genioplasty.  I perform chin implant surgery in 30 minutes or less, often using a local anesthetic alone.  In my opinion, you are a good candidate for chin implant surgery.
Hope this helps