You are getting 6 chickens, and it does not sound like you have an established flock? you are just getting started, right?
When you get the birds, LOOK carefully at the set up they come from, do the birds look and act bright and healthy? Do not take them, thinking you can save them, if they don't. This is no time for a bleeding heart, I can save them attitude. While visual is not 100%. It is a reasonable place to start.
Now, unless you have an elaborate set up, and can physically separate the birds by 300 feet, you really CAN"T quarantine. And if you can't quarantine properly, it is really a waste of time to pretend to quarantine. Now granted, you are risking bringing home a disease.... but you are risking 6 chicks, not a fortune.
People talk on here all the time about how they quarantined and how important it is..... but really they just had them separated by a wire, and different feed bowls.... they didn't quarantine, they just got lucky.
IF you have a large flock, if you have very expensive birds, well then, I would NOT introduce strange birds into the set up. Without extensive quarantine done properly. (Really, I don't think I would introduce any new birds in that scenario) However, in a backyard flock, I have often introduced birds, and (knock on wood) have got along just fine without any quarantine at all.
However, I cannot emphasis enough, do not bring home sick or neglected birds, that is just asking for a wreck.
If the lack of quarantine worries you, see if you can get all 6 from the same place. And you question about the introduction, depends on the size. If one group is quite a bit smaller, then separate them, if not, put them together. I think you are right, the strange place to all of them will be of help, do make sure that in your run you have some boxes, or pallets leaned up against the wall or some types of shelter. if birds can get out of sight, a lot of times it helps.
Mrs K