Do ducks need access to swimming water ALL day?

I have 11 chickens, and am getting 6 ducklings in April (we're probably only keeping 3-4 of them as we had to buy one of the breeds straight run so we ordered four to make sure we got at least one girl) and this is what I am thinking on a set up for them.

We have a large chicken coop with a predator proof run with a roof that is about 15x9. We'll be getting a large doghouse to house the ducks in that will open up into the run like the chicken coop does, and when we are gone during the day we're planning to let the ducks and chickens hang out together in the run. We're also building a picket fence in the front of the coop which would be about 25ftx10ft that we would have the ducks and chickens "free range" in when we're home. We have feral cats in the neighborhood so we wouldn't leave them to free range unless we were home, but I only work from 7:30am to about 1 or 2, so they would get the whole afternoon to free range plus all day on the weekends. We're planning on going the kiddie pool route to have water for them, but I am wondering if it would be okay to have the pool in the free range area, or if they wouldn't be okay without water to swim in during the early part of the day. We would have a tub of water for them that they could wash their faces and such in the run, but the big pool would be out in the fenced area.

Does this sound like a bad plan? We're planning on cutting a doorway in the front of the run and putting a door similar to the chicken coop one that hinges up to open, and bolting the doghouse to the run, so when we let the door open they would come straight out to the run. When we let them free range we'll just open the big door to the run and let them out.

This is our current coop and run set up: It looks like there is less room in front of the coop and run than there is. It's about 12 feet from the front of the run to the edge of that patio, so we'll have the fence go out about 10 feet so there is more than 8 feet between the fire pit and the fence.

Also, there is a ton of grass and clover in front of the run now, this was taken in the summer, and in the PNW summer is when everything dies because it doesn't rain much. Hahah!