Being as you are going with dual purpose birds, there is a very good chance that you will get a broody hen, even if you don't have a rooster. Go ahead and let her pretend to sit on golf balls if you want, or get some fertilized eggs. If you do the golf balls, you can order chicks to come in at about 21 days (does not have to be exact) and slip them under her at night, and in the morning, she will protect them from the flock. The chicks raised up in the flock will need no integration, and very little work for you. There is nothing as darling as a hen with chicks. Do be aware, that some might not make it, but the ones that do are vigorous. Get more or hatch more that your final wanted count, and then cull back to that. That too, is a life lesson for children.
A couple of hideouts in a the run are also a benefit. Last summer, I just laid a pallet on 4 cement blocks. The chicks could easily run under there, and while a chicken could get under there, it was a tight fit, and they pretty much didn't. This allows a place for the chicks to escape to, when they have been driving the elders crazy, and the older ones get cranky. For the most part, chicks raised in the flock are tolerated, and within two weeks, I have seen them darting under laying hens legs to eat, but I often put food under that pallet just to make sure the chicks were getting enough.
As for numbers, you can cheat in the summer. Chicks are little and take up little space, the days are long and the birds spend most of the time out of doors. Generally peoples runs are bigger than their coops. In the coop, lay a 12 in wide board across part of the roosts, and the broody hen will generally have her chicks roosting with the flock by week 4. Before that, mine have always created a nest on the floor. I tend to let broody hens do their thing where they want to, as she knows more about being a chicken than I do. But come the fall, the chicks are getting bigger, and then your count needs to be more close, and one should err on the side of the smaller flock.
As for me, my flock numbers swell and recede. And with all my careful plans, many times I have had the wrong ones die, either from predators (mostly) and twice, just dead! Be flexible, there is an old saying, "don't count your chickens until they hatch", well often times, you just can't count on your chickens to do the plan.
Note: if you hatch fertilized eggs, part of them will be roosters. IMHO - you need a separate bachelor's pad, that will allow them to grow up to eating size.
Good luck, it is a marvelous hobby.
Edited by Mrs. K - 3/23/16 at 8:59am