Does Grochatila 'listen' at all to commands? Not that many cats can be 'commanded', but my cat knows a few words. She certainly knows the word 'NO', as she is like a toddler when she wants out at night (too many things that go 'bump in the night' for her to be out...things that are much bigger than her & would win) She will either hiss at me or take a swat at my leg, then turn around and saunter away. Basically like a toddler having a tantrum! But, she clearly knows the word 'NO and, while she may not always be happy with it, she generally respects it. My point being that a clear 'NO' to her around the baby chicks and she gets the message. Someone once dropped off some baby chicks they couldn't care for a few years back and one hopped out of her arms (about 2 weeks old, so half flew half hopped); completely new to me,/us, Cleo saw it fall/half fly to the ground and ran up to it...smelled it, looked at me, and turned and walked away! I think chickens have a distinct smell, and she new it was off limits. Her turn of the head away from it, as she walked away I think, was a stress response (like a dog can't look at something it wants but knows is off limits). Could I be 100% certain that she wouldn't have pounced if I hadn't been there? No, in all honesty, I couldn't. However, given the huge amount of other prey for her....and if she had been properly introduced prior, I don't think if would have been an issue. That said, I do NOT intentionally tempt her with 'free ranging chicks' with no adult hens to act as 'guard'. I don't have any bantams, though. Also, she has been 'duly chastized' by the adults. Something like that may have to happen to him for him to 'truly 'earn their respect.
How is Grochatila around your small Rooster? I'm assuming, since your hen hatched eggs, that your Rooster has accepted her? Maybe introduce your hen and chicks to the rooster in a safe-ish (read, enclosed space with you present to observe). Most Roos will accept their offspring, imprint on them, and protect them. If he seems to accept the chicks, and your cat is afraid of him, it might work to place mom, chicks, and Roo for a few hours a day in small pen (safe one) with Grochatila able to see them (after a formal introduction with a severe 'NO' if he seems 'too interested'. That said, I still would be very careful until they are fully grown, or until the Roo takes offense at him being too close and gives him a bit of a flogging. Again, it REALLY depends on your cat!
Tax in next post..this one is too long already.
(P.S. I love Grochatila's name!!!)