Is it a good idea to get a sliding genioplasty before cheek implants?

I see no reason why multiple chin/cheek procedures should not be done in the same time. However, without in-person consultation it would be difficult to give you a more accurate advice. Good luck.

Without an exam your question cannot be answered.  You will need to see an Oral/Maxillofacial surgeon to see if othognathic surgery, genioplasty or using an implant is best for your specific case. It should be noted that patients with severely weak jaws or abnormally functioning jaws may be better treated with other facial surgery (orthognathic surgery), although a chin augmentation may be an option at a later time. These patients should seek the advice of a plastic surgeon to determine which course is right for them. Here is some information to help you make this decision: Candidates for Chin Augmentation - Patients whose chin profiles are weak but have normally functioning jaws are candidates for Chin Augmentation. Many of these candidates have used injectable fillers in the past to strengthen the protrusion of their chins, but are looking for a permanent solution. If you are one of these patients, then you are a likely candidate for chin augmentation

After reviewing your question, your goal should be overall facial harmony from all your procedures.  It would be beneficial to set your jawline initially which would mean the sliding genioplasty should be done first if you are having different surgeons perform these surgeries. You hopefully have had imaging to see what the effect of each of these procedures are on your facial harmony and balance. Good luck with your procedures.

  A sliding genioplasty can be performed on the upper jaw, the lower jaw, or both.  If you are going to perform a sliding genioplasty on the upper jaw, it is best to perform that first, and then placement of cheek implants if necessary. For many examples of cheek implants, please see the link and the video below

Whether you should make the chin change before doing your cheek is really a function of how certain you are about either change. If the chin augmentation is the primary procedure and you are uncertain whether the cheeks will need to be augmented then the sliding genioplasty should be done first. But if you are certain of both procedures then they can be done together rather than staged.