Honestly, I would just say what you wrote in your original post to the parent's. This is daycare and you did not want to hinder their playtime by telling them not to play and stay clean. I always tell parents when they sign up not to send their kids in their best clothes. I would think that if you send them home with stained pants and shoes and give an explanation then they would learn their lesson or don't care anyway. If you just sent them home dirty without comment then parents might be a bit peeved. If you wash the clothes you are just setting yourself up for disaster.