Sounds like you have it well thought out!Amiga,
Thank you for your heartfelt advise and warning!
Yes I live in the heart of the city with a postage stamp size back yard and we have a surprising assortment of 4 and 2 legged critters about.
I have first hand raccoon experience having had a rake between myself and a Daddy coon while his family made it over the fence to relative safety. Another time a young female came over the fence in broad daylight - I guess to find a home for a litter or food.
And she came back the next day while I was at work and put a hurting on my (at that time young) Jack Russell Terror.
We also have Possum and have even seen coyotes late at night in the streets.
I was even concerned about having a random red tailed hawk flying overhead while the ducklings were in the garden as they were smaller.
I have discussed keeping chickens with others who have lost them to coons.
So this weekend, I am building up a Duck Fortress for my little buddies - Bubbles and Tofu - a coop with a small run and a lockable elevated box for night lockdown.
I also plan to put wire mesh under the bottom of the entire run and surround the bottom run exterior with some 1x6 pressure treated wood wrapping the bottom wire mesh over the outside as additional chew resistance for critters on the outside (the nasty wood - inaccessible to the ducks).
If everything goes well Bubbles and Tofu will be moving outside this weekend as my wife has served them an eviction notice.
Thank you for all your help!