Welcome!!!! I have just joined as well and I am having a total blast with other chicken gals! I have a cat and when we were keeping our chicks indoors in our brooders we made a top with chicken wire nailed into wood! It was very helpful!!! also when our cat got curious I swapped him on the nose and told him no! I kept a close eye on him until he left them alone. If you cat(s) get too curious just show your cat its place.
When we moved them outside, our coop is enclosed fully, he tried to climb on the roof of our coop! we let him because we have a roof, (and also i couldn't reach that awful little guy!) Now hes perfectly good and never hangs around the coop. But i still keep a close eye on him! thats my advice... WELCOME TO THE FLOCK