Coming from someone that has many animals (specifically reptiles), what I see a lot is people jumping on small animals because they are "cute", and then dumps them as soon as they need to put in effort. It might seem fun and nice to have a baby duck now, but I highly doubt you or your parents are going to want 2 huge ducks living in your house. You have to think about the long term commitment of keeping these. Ducks can live 10 years or longer, are you going to want to take care of a huge duck that eats everything and poops everywhere in 10 years. A full-grown duck is going to need an outside, contained pen to live in, are you going to be able to provide this for 10 years? Often, scenarios like this end up with parents releasing them into the wild, which is a death sentence for them.
My personal opinion and what I would do is surrender them, you aren't helping anyone by keeping these. If you really want to get a duck, do research online and get one from a breeder, and get a species that can thrive in captivity when you are ready for it.