ZooMommy,
It's is great to see you thinking ahead and asking questions now. It may be a wonderful opportunity for you to talk to your girls about their decision ahead of time. While you could end up with relatively quiet Pekins or relatively chatty Rouens, see if you can get the girls to think about more than appearance (I know many people just love those big white fluffy pillow ducks
). Thinking ahead, and talking about possible outcomes ahead of time will be a good skill for your children to begin to develop. I am still working on the thinking ahead stuff, myself
I agree with what has been said, sounds like you'll have plenty of room. Here are some other things for you to consider:
Predators have surprised many people with how they can find the smallest point of entry into the duck pen. They are persistent. They will find the loose nail, the weak board, the fatigued wire. Is the dog pen chain link? Half inch metal hardware cloth, I would go three feet high, needs to be placed around the outside of the chain link. Think about how you are going to prevent predators from digging under the fence. They only need an inch of space and then (please forgive the coarse-sounding detail here, but I have seen the results) they can grab a sleeping duck and pull it out under the fence. 'nuff said, I hope.
Another point where perhaps most of us stumble and struggle at first is water management. Ducks are waterfowl, and need plenty of fresh water. It will stay clean for less than a minute, but that's beside the point.
Ducklings and ducks need to be able to wash their heads frequently, to avoid eye, sinus and ear infections. They do much better when they can bathe. Kiddie pools are great, and I also use concrete mixing pans (those seem to last longer). Where will the enriched water go when you dump it? What kind of slope do you have? Can you direct it toward a garden bed or compost area? Some Duck Forum members are brilliant engineers and have terrific ponds and pools. Many of us have the pans and kiddie pools that get dumped, rinsed and refilled. But if you don't have the right drainage, you could end up with a swampy area and increased risk of disease for your ducks.
I'll take a breath, now, and ask if you haven't yet, you take a look at the stickies at the top of the forum. We try to compile some of our best knowledge there.