Cage carpet is horrible if you reuse it. You will quickly find that it will be a pain to clean and will always leave a stinky smell. Meaning it can never be fully cleaned.
Personally, I prefer paper towels. Disposable, clean looking, and cheap! Although the aspen won't harm your snake. They can digest bone, I don't think wood will be much of a problem!
Your snake could for sure take an adult mouse or maybe even two! 10-15% of the snakes body weight is a good rule to keep in mind.