Something else you could try. You could get some VetRX and rub a bit of it on the top of their beak or you could do like I did and just use a touch of Vicks. You don't need a lot, just a bit to give them the smell of it. I don't think it would be good for them to eat a lot of it either but breathing in the fumes? Oh yeah.
If you are using the lower dose of the antibiotic, I would do a 10 day course. At this point I would rather err on the side of caution than not. I've read a couple of articles and reports lately that chickens can get the flu from us. Not a cold, but the flu. Don't know if it's true or not but why take chances? I've been wearing a mask for my birds if I start coughing, over kill maybe, but again, it can't hurt.
Good luck the both of you!