Whether you "need" to quarantine them is really up to you.
The reason to quarantine new chickens is to check whether they have diseases or parasites that could pass to your current chickens. It's easier to treat a few new chickens than to treat the new chickens plus your current flock.
Quarantine is especially useful if you have many current chickens, and are willing to treat and potentially euthanize any new chickens that have problems. If you only have a two current chickens, and are not willing to euthanize diseased newcomers, then I don't think you'll get much benefit from quarantining the new ones. Treating new chickens, or treating new chickens + 2, doesn't make a big difference.
So yes, quarantine might be a good idea-- but it may not be worth the bother in this particular case.
I do think that getting new birds from the same source makes a difference. They are less likely to bring in new problems. If they carry diseases or parasites, your other chickens might already have those same diseases or parasites.
In this particular case, I would probably check the new ones all over to be sure they seem healthy-- preferably before bringing them home, and again after getting home. I would probably keep the new ones in a separate cage for a day or two and then check them over again, and then introduce them to the current two. This would help you find some of the most obvious problems, while being much faster and easier than a proper quarantine.