For that many kegs, nothing but a standard CO2 setup makes sense. A cartridge system would mean hitting the kegs a couple times an hour with no control over the pressure. Plus to move soda you are talking 2-3 times as many cartridges as for beer due to the higher dispensing pressure. So, that would mean 10-15 cartridges per keg.
Even with a #5 rig, you'd use most of a bottle every day.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk