Whether you keep one or twelve, that's a generation.Sorry, one of the problems I meant is that I won’t have several generations very quickly if I minimize the number of eggs that a hen is allowed to hatch. I live in town so I don’t have space for an extra dozen chicks on top of the 15 that I ordered. So my idea of a sustainable flock is a very slow replacement, if that makes sense.
Our situations are different. I have over 2,000 square feet of room outside of the coop. I have a 8x12 feet coop and two 4x8 shelters where they can sleep. My main flock is 1 rooster and 6 to 8 hens but I hatch out 40 to 45 chicks a year. Typically I'll add 3 replacement pullets each year. Things can happen through the year where I lose some. Often that is me eating one because she did not meet my goals as far as behaviors or production. My genetic diversity would stay higher if I had more hens (more randomness) but this is how I choose to raise them. We each have to find our own way.
Not all eggs hatch. I've had hatches here 100% of the eggs hatched. I had one where 0 eggs hatched, due to an egg breaking under a broody hen and fouling the others. My suggestion is to determine the maximum number of chicks you can manage and set that many eggs. If they all hatch, you can manage. If some don't hatch, well, hopefully it is enough.I appreciate the advice about allowing a couple of eggs, I hadn’t considered a single chick trying to survive in an existing flock.
I respect Mrs. K and her experiences but this is one of the few places we disagree. Cockerels and roosters can become human aggressive, so can hens for that matter. Kids are at more risk when this happens because they are less able to defend themselves. I do not deny that life has risks. You may be T-boned the next time you drive to the grocery when someone runs a stop sign. That happened to my sister-in-law a few decades back and she is still suffering from it. She did not stop driving to the grocery store because of that.They can often become violent and tend to attack children first.
Not all and in my experience not even most cockerels or roosters become human aggressive. Some are that way when hatched, some are made that way by our interactions. Cockerels and roosters have an instinct to protect their flock. Broody hens have an instinct to protect their chicks. If we threaten the flock or the chicks we are much more likely to be attacked than otherwise. This does not mean they will always attack if we appear threatening. They will not always. This does not mean they won't attack unprovoked, some will. But the less your kids interact with your flock the smaller their chance of suffering an attack.
I don't see how letting your kids get a year older changes things significantly. I don't see how much you can learn about rooster behavior with an all-hen flock, especially when they are fairly immature much of their first year.
To me, the only reason you need a rooster is if you want fertile eggs. Everything else is just personal choice. My general recommendation is to keep as few males as you can and still meet your goals. That's not because you are guaranteed problems with more males, just that the more you have the more likely you are to have issues.
There are two general ways to get a rooster. There are variations on both of these. Some people have very strong feelings as to why their specific way is best but the reality is that we use all these methods. Sometimes they work, sometimes they don't. You can hatch eggs or get baby chicks and raise them with your flock. That's the way I do it because it fits my other goals. You can bring in a mature rooster once your girls are laying. That generally works well but some of us are concerned with biosecurity issues. Typically if your male is mature and the girls are laying, he mates with a couple when first introduced and the flock is his. Very peaceful. But occasionally that does not work, it can become violent. You do not get guarantees with chickens and their behaviors.
Good luck!