Chickens tend to be braver than you think! Household pets such as cats and dogs will soon get used to the novelty of new birds in the garden. They will potter round the garden together quite happily. We suggest that if you have any doubts as to whether your dogs will get on with the chickens, you introduce them to the dog on a lead.
We have had experience of a pair of chickens that quite easily held their own against a very determined German Shepherd puppy. A couple of pecks on the nose usually saw him off for a little while! Two or three chickens wandering around together can prove a formidable foe for sensitive noses.