I bet your ducks love those ponds!
So you've made one duck pond out of pond liner and the other is a mould is that correct? Do they have drains or how do you clean them out?
The bath dug in is a great idea and you've actually given me some ideas for my own pen. ATM I have an internal raised pond which is good but I also have two containers for the ducks for easy access next to their feeder and I was thinking of a better set-up instead of washing their large bucket out each day I might dig it in at ground level (like you've done with your tub) and put a drain in it piped out for easy emptying and cleaning.
I have 6 Pekins and I'm really fond of them - previously we started with Khaki Campbells but I prefer the Pekins.