Welcome to Duckdom!
Miss Lydia covered it all, I think, but I wanted to tell you what I used to amuse especially Acht and Eins when they were in the brooder. My runners liked to tug at the towels and sheeting I used to prevent drafts. Sometimes they'd pull things down a bit.
So I very securely tied a length of rope from the top edge of the brooder (made sure they could not pull anything down on top of themselves - ducks can get into the worst and most unpredictable trouble in less time than you can turn around). It hung down to just about duck eye height. Those two would nibble and tug on the rope (which had no loose strings they could swallow to cause impaction) for I don't know how long.
Once outdoors, they found their own sources of amusement. They like a kiddie pool for swimming and face washing, and they like piles of leaves and straw to investigate.