The ducks can go in with the chickens without any issues while they are young. However, once they reach breeding age they will try to mate with the chickens and that would kill them. Our duck actually drowned one of our chickens by pulling it into his pond with him (before we knew any better). Hope that helps!
Well I guess we will make them a small yard of there own then. No sense putting them in there to move them later. I was a little afraid my rooster might try to mate with them if they're girls anyway. LOL