Would you then, recommend day old chicks?
Yes, then I would recommend day old chicks.
Now day old chicks have their own problems. You must raise them separate from the flock, and you will need to keep them separate for about 4 months. At that time they will catch up to the older hens in size. Integration can be tricky, and there can be lots of fighting and pecking on each other. The close they are in size, the less there will be. One should get at least the same number of new as the old flock, or even slightly more, that will help with the integration.
It looks to me (I might be wrong) but are you a first time chicken lady? If so, you probably don't have any of these birds laying yet. Please don't think I am presumptuous and am telling you what to do, however, you might consider waiting a year to add to this flock. There is a learning curve to this hobby and it is best not to rush it all at once.
Time allows you to test your set up, find weakness in your run/coop, deal with predators and figure out how many eggs you really do go through, how much the feed bill will be. Figure out what you really like, and what you don't.
You did not state your breeds, but some breeds tend to go broody. If you do have a breed that goes broody, she won't probably do it till next spring. At that time you can order fertilized eggs to put under her, or buy day old chicks to put under her...... she can raise the chicks right in the flock, and there will be no integration problem. You do not keep them separate. That is how I love to do it best. It is fun to get new kinds of chickens. I love my flock, but the birds in my flock change fairly regularly, most flocks do.
Now, one must seriously consider a doable plan if you get roosters. If you get hatching eggs, slightly more that 50% will be male probably. If you order or get chicks from a farm store, 10-50% of the chicks can be male, sexing chicks is not perfect. One should not have a lot of roosters unless one has a huge space and lots and lots of birds. So you need to have a plan on how you will cull those birds.
Chickens, even nice chickens are not always nice. They are chickens and act that way. Even chickens that are well cared for, handled often and spoiled sometimes turn very mean to other chickens or to people. This a fact of chicken raising. It is very helpful to have a plan in place.
Mrs K