want to introduce two new ducks to flock, same age, sex and breed as existing

[Nandinaberry]

The many threads already posted have been very helpful about introducing new ducks, but I still have some questions.
I have raised three female Cayugas together since they were a day old. They are now almost 2 years old. One died about 6 months ago, and the two left have been getting increasingly loud and competitive about being the sentry duck, trying to out-quack each other over every little thing. The third duck helped create a democracy, and they were very quiet then.

I am thinking of adopting two more female ducks, retired breeder Cayugas from a commercial farm that are between 2 and 3 years old.
Coming from a breeder, will they need to be quarantined?
How will they adapt to the sudden change in feed and environment, and how can I ease the transition? They will have free range in our large suburban garden and a varied diet of organic feed and greens, worms and other insects. At night we lock the ducks into their enclosed pen, swimming tank and house safe from raccoons and possums, but I'm concerned about putting them all together in there without some separation at night. The pen is left open during the day so the ducks can come in to eat their feed and greens and swim if they want. Should I keep the new ones locked in the pen during the day for a while?
Most importantly, how long do I need to keep the new ones separated from the others? Will a group of females get along better than if there were a drake in the mix? How long will it take them to adjust to their new surroundings/lifestyle, and is that too much to ask of a duck that has spent its life in a hatchery?

I keep wondering if they will all freak out and then I'll have an even hotter mess to explain to the neighbors!

 

[Onlyducks]

I don't know about quarantine.

My muscovies were fine even after being driven 150 miles in the back of a pickup to my house from the breeder and putting them into a pen. I left them in the pen for about a week before letting them free-range in my garden and then in my yard. I then put 8 weeks old pekins in a pen that ajoined the muscovie pen. I let them look at each other for a week and then let them all free range. That was about 6 or 7 weeks ago. They free range just fine, like to check out the other breed's pen in the daytime and ignore each other much of the time. The pekings are not of mating age, and since I have four males, that may prove interesting. Ducks are actually very adaptable. The muscovies were free-ranging at the breeder, but when I brought them back, they liked the pen and food delivery idea! I actually had to shut them out of the pen to get them to free range. Most things seem to take a week or two for the ducks to adjust to and then they're fine, in my experience. I think the owners suffer more anxiety than the ducks. I used to be so nervous when I put the ducks out for the first time, etc. Now, I guess I've seen how easily the ducks adapt and I'm much more mellow.

 

[Nandinaberry]

Thank you for easing my mind about the ducks' adaptability! Even though mine compete with each other, they've never hissed or pecked at each other. One day a male mallard flew into our yard and tried to flirt with them for quite some time. They were curious, and then just ignored him, even though he kind of chased them around a bit. And he was so cute, too. A dandy Mr. Wilkes Bashford, but they were not impressed.
I'll try the week-in-the-pen idea. I have a way that they can all sleep in their house, but separated, too, for awhile.

 

[Nandinaberry]

And what about feed? Did you transition them from the feed they were eating before, or just start them on what you already feed your other ducks?