Sagging cheeks like a bulldog - what can I do? (photos)

Based on your photos it seems that you are an excellent candidate for lower face and neck lift. This procedure will allow removal of jowls and tightening of lower face and neck to give a definition to a jawline. This is achieved by tightening and lifting deep structures of the neck and face (SMAS). Addition of volume by means of fat grafting or soft tissue fillers to selected areas of your face will further enhance the results of lifting.
In-person consultation by an experienced board certified plastic surgeon with good reputation in facial rejuvenation should be your next strep. Good luck.

The good news is that the kinds of problems you demonstrate in the photos, which are seen daily by those of us who specialize in aesthetic medicine, i.e. the loss of volume, especially in the infraorbital region and the upper inner portion of the cheek (on the side toward the nose), the deepening smile lines and marionette lines, the incipient jowl formation along the jawline, the loss of volume in the upper lip ( in particular), and the development of "bar code" (aka "smoker's lines" or "lipstick bleeding lines") above the upper lip, and the suggestion of some downturning of the outer third of the eyebrows are ALL easily amenable to the advanced uses of injectable volumizers and fillers. In experienced hands, treatment of all the above should not take more than about 45 minutes without the need for cutting, stitches, or any significant downtime. I would suggest that you check out the archives of RealSelf.com using the search terms: The Nonsurgical 3D Vectoring FaceliftThe Nonsurgical Treatment of Under Eye Tear Troughs, Hollows, & Dark Circles; The Nonsurgical Mid-Face Rejuvenation; Nonsurgical Lip Augmentation; Fillers For Treating Fine Lines & Crepeyness; The Nonsurgical Treatment Of Jowls Along The Jawline. For most of the procedures the results engender an immediate "Wow!" reaction.  So, don't despair. Just do your homework and then your due diligence in finding a board certified aesthetic core physician. As part of your vetting, be sure to ask to see his/her before and after photos for the treatment of each area. Best of luck to you.