I ended up adding the peanut shells to the litter on the floor. We have a deep bed of coarse bark on half of the enclosure so I just tip it on top, the girls come running and have a good peck and scratch, and it gets mixed in nicely. Adds smaller, softer bits to their litter so it's easier for...
I didn't think they would be terribly nutritious, but using them as bedding sounds like a plan. I was mainly worried that they could be toxic :) Thanks for that