When my mom did daycare, we just used "NO". They didn't understand a whole sentence like "You have to be nice otherwise the kitties get hurt" .. they would just stare at us like "yeah sure big person.. let me play with that furry toy" After a while, they would ask.. like point to the kitty and say "Ta?" or something like that, and we would say "yes.. gently.. " and show them how to pet. It would be tragic if the kitty got so fed up it turned around and scratched Dylan.. especially in the eye or something like that. You might have to take the "NO" route. Good luck though!!