I certainly do have destructible toys for them. I have a string of soft-wood plugs that they absolutely love to chew on and shred.
As you can see, it's much loved and much chewed by both Mab and Titania. As a matter of fact, one of Mab's favorite games is pulling fibers off the plugs and seeing how much of it she can fill their birdbath with.
To date I have never seen them bathe in it. It seems to be a secondary drinking bowl/wood fiber depository.
Another toy I have that they adore is this monster.
The device Mab is currently cleaning herself in front of is a wicker ball full of tissue paper streamers with a bell on the bottom. This seems to be their all-purpose toy. They tug at streamers, climb on the wicker, pull twigs out of the wicker, play with the bell. They adore the thing. There's plenty for them to shred in the cage without resorting to the liner. The issue is the cage liner has a plastic layer on the underside to stop moisture seeping through and I don't want them ingesting that. Any tips?
Edit: Mab also seems to be chewing on the edge of their food bowl which is also plastic so I'm not sure what to do about that either.