Might find something to your liking here
https://www.backyardchickens.com/newsearch?search=Duck+house+and+run
Ducks are very hardy and won't need supplemental heat as adults but good ventilation is a must just as with chickens. Their house should be close enough to the ground that they don't need to walk a long ramp or steep ramp but a wide ramp will be okay as long as it isn't steep. according to Storey's guide to raising Ducks which all duck owners should get says large ducks need at least 6 sq ft of floor space per bird . Run needs to have at least 10 sq ft or larger if you can per duck
Ducks love water so a kiddie pool they will love you for but as ducklings they will have to start with something like a cat litter pan with something on inside and out to help them get in and out bricks or large stones will work. Never let a duckling sit for long periods of time in water they can chill and die which means until they are feathered in someone should be with them anytime there is water deep enough for them to get into. The need to be able to dunk their heads everytime the eat to keep their nares and eyes clean. so some kind of water bowl that they can wash in with out getting into I'll get you a pic. Ducks are very messy so it's a good thing you don't intend to leave them with the chickens because they will muck up bedding pretty quick.
Matter of fact I would be extremely worried about leaving ducklings in with chickens, chickens can be very mean to ducklings even to killing them so If I was you I'd give the ducklings their own brooder away from the chickens, once the ducklings are larger then free ranging would probably be fine, my ducks chickens and geese all free range together but they do not sleep together.
https://www.backyardchickens.com/t/750869/raising-and-caring-for-ducklings#post_10611711
Love to see some pics
