I used to keep ducks myself years ago, so I totally get what you're in for. One thing to keep in mind: ducks are
fantastic at turning a nice patch of grass into a muddy, poopy, smelly mess — and fast. Since you've got a sensitive flock, it's worth noting that all that moisture and manure creates the perfect environment for parasites, bacteria, and other not-so-lovely microorganisms to thrive.
To keep things healthy, you’ll definitely need to rotate the Omlet enclosure onto fresh ground regularly.
However, that comes with a new concern: as you move to new areas of pasture, you're potentially introducing your birds to spots where wild birds may have left droppings carrying avian flu, if you are worried about that,
or just looking to meet the legislation requirement.
Consider:
Before relocating the enclosure, consider
lightly spraying the new area with a bird-safe, plant-safe virucidal disinfectant. Products containing
citric acid blends, or hydrogen peroxide-because it damaged the virus cell- can sometimes be used at low concentrations to reduce (not eradicatee) pathogen load without harming your grass.
It's not a perfect shield, but it adds an extra layer of biosecurity, especially in high-risk months when migratory birds are passing through.