I house both my ducks and chickens together and have for years. Never had an issue with multiple generations, with the exception of a white crested male duck that fancied two white hens. He thought they belonged to him and would drag them around by the neck. If you coop them up at night together and there is an aggressive duck it wouldn't take you long to spot it. If you want to check for lice it's very easy. They are usually present on lower back just above tail, around vent area, and under neck. The eggs cluster around the base of the feathers and the lice are tiny little oval shaped light brown or cream colored translucent bugs that scatter when you spread the feathers.
This shows both the egg clusters and bugs themselves. Very easy to search for. Just spread feathers around vent, around neck and just above tail. They will infect those places first typically.
Now if you want to check for mites it's also equally simple to check for. Here is a link that explains everything.
There are different types of mites, but they are typically small and brown.
Hope some of this info helps!