I have trained a few bird dogs, and they always perform a bit different with other dogs around. Not always bad but different.
That being said get the two dogs together, before you hunt, see how they act together. Play fetch with the two of them, do your drills etc. I have seen pups that were just too distracted by other dogs. My current dog is sort of competitive, and I hunted her with a buddies 100+ lb. lab her first season and she had an if he can do it I can attitude. Now it really doesn't matter if there are other dogs once the first shot is fired nothing else matters to her.
It will depend on their personalities and such, but usually once they realize what they game is nothing else matters.
BTW don't put her out on geese until she is really into the ducks. A buddy had a pup that he sent out on a wounded Canadian goose, that goose stuck the dog hard enough to draw blood, and the dog hasn't retrieved a bird since. Sometime wounded geese get nasty with the dog.