I use live ducks all the time. I will remove the flight feathers from one wing and use duct tape to create a flap on each foot. This will prevent the duck from flying away and prevents him from diving very long. I have seen folks that tape the wings and feet, but I don't like it.
Every dog is different, so you need to decide when your pup is ready. I've done at least one duck chase by 6 months with my pups. A well bred dog shouldn't cause any issues as their desire for game will overcome any negative experience.
Good luck