Hello and welcome
Your new arrivals sound exciting!
In regard to space my advice would be "as much as possible".
If they are on pasture/grass (which is perfect for them) when it rains they will dibble and turn areas into a quagmire no matter how much space you give them. It's not the walking in it, it's them drilling holes and sieving through the mud. Rain will settle anywhere uneven and that area will soon become a muddy mess. If you have the space it is a great idea to have two sections that you can rotate so the other had a chance to recover. I have 20 ducks and they have two pond in the space of about quarter of a football field. It still gets really muddy in the winter. If you have good drainage then you may find it easier.
Very important for ducks is cover, they love trees and low bushes, it makes them feel secure and they can get shade from the sun. They will also need a protected dry area for their food and somewhere outside they can shelter from wind. They don't usually like to go inside unless temperatures drop well below freezing.
Good luck and keep us posted!!
Zo
