My barn cats never bother the chickens. As a matter of fact, when I see mouse evidence in coop, I put a cat in there for the night. Two of my best hunters were actually raised by a rooster. The rooster saw little yellow fluff balls and adopted them. He was a very good daddy too. He was mortally wounded when 2 dogs came in the yard and he fought to protect them. But, back to the subject at hand, we have never had trouble with cats.
My cat knows he is allowed to watch the chicks when we clean the brooder, but not allowed to interact with them closely yet. He does not make the usual stuttering "me me me meow" that he makes outside when in hunting mode nor are his muscles tense at all. At night he lays down on top of the brooder and the chicks sleep directly under him. He gets upset if you move him and the chicks wake up and then no one gets any peace for at least an hour. By the time the Buffs are "all growed up" They will be bigger than he is and I very seriously doubt he would attempt to take them on, especially Peep, who at two weeks intimidates the dog.
Haven't had a problem with cats and any chicks yet. Never had a problem with adults and cats. A new stray decided to watch the baby chicks run about, but a stern yelling and pointing later, the cat ignores them now.
I also have 2 outside cats and they do not mess with my chickens. I only have small silkies so they would be an easy meal. My neighbor's cat comes over and watches my chickens but seems to enjoy the company. Right now I have 6 three day old chicks in my backyard with their mom and my cats are right there in the same area and could care less about the chicks. Although I do seem to have very lazy cats. Ha... Ha...
I would just take it slow in the beginning and be there to observe.
Good Luck!!!!!
I have a "stray" (used to be I guess) who actually insists on being locked in the coop with the chickens every night. She absolutely adores the chickens....rubs and snuggles them all the time.