I've have had it both ways. I started out with ducklings, but I got them straight run and ended up with 5 males. I rehomed three of them, and have since adopted 6 laying females. They were in need of a good home, and I didn't want to go through the mess and time of raising ducklings again. They were all already laying eggs, so it was nice to have eggs tomorrow, rather than waiting 6 months. If you do get adults, please only get one male. It is hard to have a happy flock of several drakes, especially if they weren't raised together. There could be a lot of fighting before they figure out who is in charge. Females are different, they seem to accept each other fairly easily. There will be some minor scuffles, but nothing like competing drakes.
I think everyone should raise ducklings at least once. It's amazing. But you could get the adults now, and have ducklings in the spring.
And yes, you can eat fertile eggs. As long as you gather them daily, there is no difference than unfertilized eggs. A cell may have divided, but I doubt you would be able to taste it
Most of our eggs are fertile, but we eat every single one, and sell our extra.
Edited by jducour - 10/8/15 at 2:08pm