They are edible at any size.And yeah, I feel bad but my cockerels are starting to look delicious...like little Cornish game hens.
If you are impatient, you could butcher one as soon as you like. Of course they are quite small now, but you could start learning butchering skills. And butchering them at different ages helps you learn what ratio of tenderness to size is best for you (younger is more tender but also smaller.)
(I've butchered banty cockerels before they were even 8 weeks old, if they were too noisy or getting crowded. There's not much meat on each bird, but they're probably just as big as the quail some people raise for meat.)