I freely admit that I am still aged 3 at heart, and love calling things like my children's toys "birdy", "liony", "snakey" etc.
It sounds very cute, possibly quite childish, and probably a bit silly. Obviously if I was actually aged 3, this would be fine. But being 40 years older, I do feel.somewhat not really convinced it's something entirely appropriate for a middle-aged woman to do. I think it's ok in the context of age-appropriate conversation with my children, but not really anything other than this.
My point of this rambling reply is to say that Ducky is cute in terms of a small child's name for its own cuddly toys, but it is probably pretty much just embarrassing for a name to call a baby who will live its life with your choice.
Unless of course, you love the regional slang stereotypical phrase "Aye up, me duck!", in which case, it's possibly the best name ever.