like Goosepimple I wouldn't want to pour too much water on the idea and I am aware that it is possible to keep hens happily on fairly small areas provided they are given all the necessary as far as food, shelter, space to spread wings and a chance to scratch around in the earth. the paving slabs don't sound ideal with or without sawdust/ if its not possible to get rid of them I spose turf or a few barrowloads of soil would at least provide a better surface.
our animals all muck along together now but the dogs, cats, chickens, sheep pigs etc have all taken time to get used to each other. a dog haring by each morning is bound to scare them initially. I guess if its a once a morning ritual and can happen before they are let out then it might reduce the possibility of them being unduly bothered by it