My experiance may help you.
A couple years ago in the spring I went to the feed store with my kids and they happened to have tons of colored easter chicks and ducks. I was very pregnant, their father had left us a few months before, and my parents had just moved in with us. My little girl and son spotted those baby ducks and desperatly wanted them and I just didn't have the heart to say no. Plus my mom loves ducks and talked about wanting some one day. So I gave in and, completely unprepared, came home with two little ducklings and no idea what to do with them.
Long story short, a few days later through a series of mistakes with overexuberant kids, the dog played with one while we were right around the corner from her and killed it and while we were retrieving and checking out that one, quick as could be she managed to get the other. No blood, just broken necks.
My kids knew what happened so I had to explain that the dog was just playing with them and didn't mean to kill them and that it wasn't really her fault, it was ours. We buried them and my kids were really upset. I kept explaining to them that she wasn't a bad dog and about instinct...
I was torn about what to do, I ended up not getting new ones because I didn't want to make my kids think life was such a disposable commodity that when something you loves dies you just go out and buy a new one, it also proved to the kids that they were not responsible enough yet to have a pet.
The kids still remember the ducks (they even attempted to dig them up before I explained why they couldn't
) and the lesson they taught them. It was definately a life learning experiance.
We made sure we were fully prepared first and we recently got 26 chicks and the kids are really protective and careful of them and always making sure they are closed in safely and the dog cannot get to them and much better about being responsible with them. They even chewed me out when I left the door open by mistake while changing their water