I would NOT be letting any child (other than if it was my own) to go pants-less in MY home. Parents do NOT have the right to tell me what to do in MY business. I AM THE BOSS.

I would tell the parents that when I personally see the signs of the child understand the concept, I will try it out (but after the parents have been successful at home for min of 2 weeks and no accidents). As a provider, I will help, but NOT take on the job, as I am NOT the parent!