My son is like that too. I just ignore it. I think he'll grow out of it himself. Meanwhile, I just say "good-bye" for him.

I think it's really important to teach children how to say good-bye and thank you. I start teaching this to my kids when they are only 2 or 3 years old (depends on their language skills!). As they grow older, they just do it automatically. I think it gives them confidence when they can look at the hostess and say, "Thank you for having me." If you teach your son how to do this, he'll be less shy in the end.

I disagree. I have a shy little boy and if I try to make him say anything to a grownup he just gets more anxious and withdrawn. I think some kids have more anxiety than others. Most of them are a little overwhelmed by adults but they might be able to say good-bye to their friend instead. Some will learn to say goodbye to an adult but some need more time. I know my son cannot be pushed and I don't recommend pushing any frightened child. As for most parenting issues, patience is required. They all grow up in the end.