With the Swine flu as a threat this is a very smart thing to do.This may sound strange, but before I let the kids play with them I spray them with a disinfectant spray. That way if there are some germs on them, the germs are gone.
Here is a good link that will give you a step by step description on how to do it. I think it's kind of a neat idea.http://www.yougrowgirl.com/thedirt/2007/04/13/toilet-roll-seed-starter/You can also start you carrot seeds in tp rolls. When they've sprouted the entire roll goes into the garden. It will degrade as the carrot grows.