If you can get a few bales of straw and pile in there they love to jump on that, and fly off of. AND tear it apart and eat any seeds! My kiddos destroyed a straw bale in a couple hours at Christmas! Made a terrible mess but they had fun doing it!
If you can get even hay bales - 3 stacked 2 on the bottom and the third on top like a pyramid they love to jump off that - I also put 2 on the bottom and leave a space between them and place a third as a bridge across the top

Great place to poop on also hahaha!
A step ladder is also fun

my 3-step ladder seems to be a great place to jump up onto poop on and then jump off hahahaha.
I see the barrels in your run - do they like to jump on that? it looks way too clean

mine would be covered in doodoo in no time!