You will never know what happens if you don't give it a shot. If the chicks don't make it, then its no use trying to hatch any more giant eggs. But if they do, and you get a giant chicken, it would be the coolest thing ever. Also, ducks don't lay eggs the same color 100% of the time. It MIGHT be a duck egg. A good way to tell would be to run some of it under water. Duck eggs are water proof. However, if it is a chicken egg, this will damage the protective outer layer of the egg and allow bacteria to seep in and destroy the embryo. Its your call in the end on what you decide to do, but i say go for it!