After reading all your answers we have come to the conclusion that we will continue to teach our children to use Mr. and Mrs. when talking about or to our non-Amish friends. Maybe with some more practise it will come to feel like the proper way, and hopefully it will make it easier for our children if they ever have a family of their own.
I find it very interesting how different cultures have there own ways of determining what is acceptable and what isn't. For example: The community my husband and I were raised in, it was considered highly improper for men and women to visit with each other if they weren't related. And children did not address or start a conversation with grown ups.
When we moved to this area we soon learned that there those guidelines of conduct were unheard of and I found it very annoying when children came to talk to me and ask me to hold Sunbeam, who at that time was only several weeks old. There were many other things but they can wait to be discussed until a later date.
Thanks again to everyone who took the time to answer my question.