In my view, children don't often use adults names anyway - they usually refer to people as "Billy's Mum" for example. Friends of yours should be seen by the child as friends of theirs too, so Christian names, in my opinion, are respectful and personal. I wonder if it's respect or good manners you're wanting your child to develop? Respect has to be earned where as good manners are learned. Holding doors for adults, not butting in when adults are speaking etc are god manners and therefore being respectful to adults. Being a teacher with my daughter (age 5) at the same school as I teach in, has made issues of respect arise in our home too. My daughters friends (and their parents - who are also friends of mine) refer to me, when at work, by by formal name, and when out of work by my Christian name. It demonstrates a distinction between work and leisure.