I use Trifectant (a/k/a Virkon S) its about the best there is. Doesn't harm
finishes and its safe to use around kittens. As with any cleaning product,
try it out on a small area- just to make sure. Kills feline parvovirus
(panleukopenia/distemper), herpesvirus, calicivirus, ringworm and a host of
other viruses, bacteria, fungi & Mycoplasma.
Here's the spec sheet
http://www.maxshouse.com/Equipment/Trifectant_Spec_Sheet.jpg
.
The only downside is the solution only lasts for 7 days after its mixed.  I
use the tablets to make up small quantities- 1 tablet makes 16 oz, or 2
tablets make 32 oz to use in spray bottles. Just drop the tablets in a spay
bottle with 16 or 32 oz. of water and you're good to go after it dissolves.
For larger areas you can order the 1.3 oz packets that makes 1 gallon and
treats about 135 sq. ft.  Trifectant also comes in 10 lb. tubs- but for home
use, you're better off with the tablets for spay bottles and 1.3 oz. packets
for mopping solutions- no measurement.

Here's were you can order Trifectant in tablets and packets:

http://lambriarvetsupply.com/sbsite.php

http://tinyurl.com/9u3fk

Btw, you might want to separate the litters to limit the spread of disease.
If you can, keep each litter in a separate area- or better yet, in a
different room.

Best of luck,

Phil