yes; I've done it two years in a row; They can eat the same food, and the ducks will grow much faster than the chicks, and will be bigger than they are in a couple of weeks. Good luck
I've raised them together until they reach a certain age.
Ducklings are generally messier, especially when it comes to their water dish.
I don't fill my waterer up completely, about halfway, so that the ducklings don't make a mess out of it, and so that the chicks don't get soaked and cold.