What do I do about these Malar mounds/festoons on my cheeks?

You may be a candidate for non surgical treatments like dermal fillers or other treatments like fat transfer to help address your concerns.  Arrange a consultation with a fully qualified plastic surgeon to discuss your options.

There are several different approaches and your oculoplastic surgeon should be able to go through them with you.It may take a combination of approaches over time. Fractionated CO2 laser has worked for me as a surgeon and patient.Fillers in other areas, blepharoplasty, micro-needling with PRP, IPL all may have roll.

What you have is neither festoons nor malar mounds by normal definition. You have a double orbital ligament attaching external to the bony rim whit the medial one extending significantly downward, You also have a low attachment of the zygomaticus minor muscle, causing a depression between the ligament above the muscle and the orbital rim. This lack of soft tissue in the area (a congenital variation) causes what you see. This is somewhat harder to deal with than the "usual" tear troughs, as you have to fill above the ligament, something we generally avoid using fillers, but something that can be done by placing the filler on the bone where the muscle normally sits if done carefully. If done surgically. the orbital septum has to be divided low and the fat draped over the anterior orbit to fill the area. Make sure yo see a very experienced plastic surgeon who is an expert in both fillers and eyelid surgery.