Ok, wait. "The wood shavings are not good for balls"? What kind of wood shavings are you using for your mice? Generally speaking, if they're not good for balls, they're not good for mice either.
The main thing you have to watch out for is the oils in softwoods such as cedar and pine. A high quality kiln dried pine shaving should be ok for mice but not the snakes. Never use cedar for snakes, mice or rats.
Aspen shavings are ok for the mice AND the snakes. (I use it for both).
With all that said, I don't really like having the rodents in the same room with the snakes, but I currently do, and I'm not experiencing any problems at all.
Steve