Man! They sound like kids!

Have you tried a bunny hotel? That's a good-sized carboard box inside another, with entrances cut so they can run in & out; kind of simulates a warren. Then they could chew on that if they liked.

Sounds as if you've already tried most other positive alternatives. May be time to go with a little behavior modification or negative feedback.

I'd be very careful about this--you don't want to use anything that would actually harm their little mouths or noses or eyes, or be toxic to them (and lots of stuff that won't bother us is toxic to rabbits)--but I believe that it may be possible to discourage them from chewing on the wrong thing with a judicious application of tabasco sauce or something to the baseboard or carpet edges. Supposedly they can learn pretty fast from a negative experience--especially if you offer them a fun alternative like the bunny hotel at the same time.

Be sure to get more exact advice on this; you may need to dilute the tabasco or use another product that they won't like. But if it tastes bad to them or they say "Ooh--that's too spicy! Where's my water bottle?" it may teach them pretty quickly that this is a bad thing to chew on.

Good luck!