My chihuahua and chihuahua/doxie are completely trustworthy with my chickens.
HOWEVER, they were both raised from tiny pups to respect and NOT TOUCH smaller animals in our household. It's been ingrained in them from day ONE that they may look at small animals, even sniff them, but they CANNOT TOUCH.
I keep a large number of animals, ranging from chickens to goats to lizards and snakes, so this was important for them to learn.
They will follow a chick around if it gets loose. The doxie mix will look at the adult chickens and maybe even give them a sniff.
The chihuahua is TERRIFIED of adult chickens.
Can't say I blame her, they're MUCH bigger than her.
(For the record, they are never left alone with smaller animals regardless of their training. There have been times, however, that I came home to a loose chick that has been followed around by them out of curiosity. I use this to my advantage, because they will "show" me where the chick is.)
So, to get to your questions, it can be done, but in your case, I think its better to err on the side of caution and just ensure they never have contact. Depending on your pups sizes, the adult chickens might be more worrisome, as they're more than capable of giving a small dog a pecking or thrashing it won't soon forget!
Good luck!