Hey there Molon! I am in the same boat current as you and wanted to see if you made a decision on your flooring? I am in the waterproofing industry and know the dangers all of their material data sheets say. I have been going around and around trying to make the best decision for my girls and i think i have come to the conclusion that nothing is 100% safe and all we can do is the best we can.
With that being said, i bought a gallon of the Flex Seal last night from Lowes (
https://www.lowes.com/pd/Flex-Seal-...fl-oz-White-Dip-Rubberized-Coating/1000097850 ) and will be going with that for my OSB floor board coop and then aspen shavings over the top. It will be non-slip, easy to clean and will seal all of the cracks from bugs and drafts. It is advertised as non-toxic and safe for plants and animals. However, it does say on the side that it has Toluene in it which is linked to birth defects and other side effects.
Everything except straight plywood on this side will have similar side effects so at the end of the day a decision has to be made and this is the one i am going with.
I wish you the best in your decision as well