I'm 45 and have what I believe to be malar /festoon mounds, Treatment options? (photos)

This area is hard to treat with reliable results. Lasers are one option that patients have used for improvement in this area. Another newer option is Morpheus8. These treatments done in the office can stimulate the body's collagen production and improve tone and texture.

there is no cure for festoons but lasers over time shrink them and plasma pen is very useful. at home peels like aerify should be done monthly, enlighten or cosmelan every 3 months and dermarolling weekly.

at home peels like cosmelan, enlighten and aerify along with dermarolling (emerageskin roller with anteage MD ampules) should be started now. 

There are many things you can do to treat under eye hollows and dark circles. A surgical option to remove skin and/or fat will such as lower eyelid blepharoplasty with or without fat pad repositioning will be the best long term. There are many things you can do to treat under eye hollows and dark circles without surgery. Non invasive less downtime options such as fillers, lasers, microneedling/PRP, cosmelan peels, and microneedling RF like Fractora or morpheus can all help give some improvement. Accutite can often be used or stronger lasers like erbium or co2 spot treatment can tighten the skin and give very quick improvement in wrinkles and texture. I suggest you get a formal consultation to see what is best for you and your goals. Best, Dr. Emer.

I would recommend a consultation with a laser or energy based device specialist (high end medical spa / Derm / Plastics) and/or a plastic surgeon for a recommendation on surgical options.
I think that the former (energy based devices) can provide some real benefit to help tighten the skin in that area, while surgical options may provide the greatest result.
I would avoid injectable fillers anywhere near this area. Fillers will only make it worse IMO. If you have done injectable fillers, I would consider trying a dissolving agent in that area in an attempt to see if it improves, but based on photos energy based treatment is probably best (RF micro needling, fraxel, etc.)