Uumm I live in FL on an island, yep have lots of sand around here so very aware of what sand can and can not be. We also don't use coops like northerns do.

all open air, under roof pens. No runs, no coops like most think of. The pen doors are opened allowing free range into the pastures and yards. So all of their (what you would call coops) are sand floored. They work great too, rake level again after they dig their dusting holes, spray down with water in the hottest months to give an extra cool place to cool down. All of the goose houses have sand floors with hay added on top for nesting/padding. We can't get straw here, so hay is used in its place. How we house the birds doesn't work for everyone, but it works very well here on our island in high heat and super humidity with severe summer storms to include hurricanes.