Fans will move cold dense air better than warm less dense air. The motors will age slower in cool air.
Suggest mounting small fans below coils, pointing straight up. The jets from these fans will move much more air than just the air that goes through the fan cages, and allow air to move freely when the fans are off.
Make some electronic savvy friends. They can make a cheap field effect transistor work as a voltage controled relay to turn the fans on/off without drawing any current from the solenoid circuit.
You can add a thermal switch in line with the FET in the range of 80-90F on the cold side, but you can find inexpensive adjustable thermostats on eBay and Amazon that would allow you to fine tune with experience.
Clean the dust off the coils and make sure ducting is well sealed and shaped to manufacturers specs and you should not need fans unless you spend a lot of time in hot weather.