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. 

The photos suggest volume deficiency rather than festoons. There is a prominent trans cheek furrow which delineates different fat pads in the cheek. You would likely do well by starting with one vial (1 ml) of a medium type hyaluronic acid gel such as Restylane with lignocaine, delivered via a single entry point and canula on each side. Then see how it is about a week or ten days later and decide if you require a second vial.

Festoons can be tricky to treat appropriately - fillers alone typically don't work well.  A combination treatment is the best option - this includes reduction of the fluid that is built up in the area (avoiding salt, too much alcohol, smoking, etc), gently smoothing out the irregular areas that remain with either fat or filler in the high cheek area (Sculptra works great for the cheeks), and a topical skin treatment (lasers or chemical peels).