If you can provide closeable vents, it is sort of impossible to have too much ventilation for a duck house (if you can close them against weather)
They might appreciate a heat lamp in real cold weather, but they won't DIE without it. Depends on how much like the 'Duckdorf Astoria' you wish to be!!!
Heat lamp not neccess., may I chime in; neither is a heated water thing, if you are willing to check on it during the day, adding hot water, etc. They can go without water a little longer than we might think.
You can certainly use a wire floor. But skip the chicken wire. It should be 1/2 X 1...