Don't give kids an apparent choice where there is none. Instead of "I would like" you must make it clear: "You must always..." If that seems harsh to you, give them a choice of two things that YOU decide are acceptable. "You can either knock on my door, or call me at _______ to get permission to come over to visit them." Never let them assume there is wiggle room for a choice of their own. That's not being mean, it's being responsible and honest, and it can be said kindly (but firmly.) BTW; regarding the description of "your" wildlife--can I come live with you??? 
