Sorry for your loss

Do you mean you're going to incubate them or that you're wanting a duck to go broody? It sounds like the latter. If the latter, the duck needs to sit on them 24/7 with the exception of a brief break or two each day to eat and drink. You can't make a duck go broody, and leaving two eggs might not get her to do it - most ducks don't sit until they have what they consider a full clutch, which is not usually only two eggs. Breed plays a role too - what breed is the female you are hoping will sit on the eggs? Some breeds go broody while others generally do not. You really only have about ten days to start incubation before the eggs begin to become less likely to hatch, so if you really want to hatch them, you should really be looking into getting an incubator and doing it yourself. You may also want to do more than two eggs since there's no guarantee that they will both hatch and if only one hatched you'd be stuck with one lonely duckling.