Hi, TayAshley! Welcome!
Are either of your kitties showing symptoms? I'm thinking that if there was little Coccidia in the stool and they don't have active cases of diarrhea, they may just be carriers and won't get sick. Unless they've eliminated outside the litter box, they've probably not contaminated the house much--the Coccidia is shed in the stool. I'm thinking that just a good washing of the floor might be sufficient to prevent reinfection. I'd also be changing the litter frequently and maybe bleaching the litter boxes more often for a while.
At one point, we had 8 housedogs--and occasionally one or two of them would come down with coccidiosis. The initial infection was from outside--they tended to eat things they shouldn't have when they were younger.
We never disinfected anything inside unless they had an accident--and outside, we just made sure that all feces were cleaned up as well as possible immediately. When they still were in the diarrhea stage, we used a very dilute bleach solution to soak the immediate area of elimination. But none of the other dogs would come down with it, even though it's highly contagious--so they didn't seem to pick it up from surfaces inside the house. The Coccidia that infects cats is different from the one that infects dogs, though, isn't it?...so maybe reinfection is more common in cats than dogs? Did your vet recommend that you try to sanitize the floors?