Would you recommend fillers to fix a 24 year old's festoons? (photos)

Juvederm can work reasonably well in this area and may last 6-9 months.   You may consider several treatments with juvederm, but may want to consider fat grafting to that area for a longer term solution.   Fat grafting can fill the concavity, will last much longer and should remain for many years.  

Despite your young age, you have depressed areas in your cheeks which are of aesthetic concern.  These areas are largely due to changes in your underlying facial soft tissue anatomy.  They can be difficult to correct.  I do find that injectable fillers such as Perlane or Voluma can be of benefit.  As this is a more complex condition and then some I would make certain that your injector is extremely experienced and his treated patients with this condition previously.  Best of luck.

You have a prominent malar fat pad.  These can be tough to eliminate.  If you put some filler in just below it where it is hollow you may be able to smooth out the transition so you don't notice the malar fat pad.  Sometimes some laser on top of the fat pad may help to tighten the skin and flatten it a bit, but results are variable.