DS (nearly 5) has an imaginary friend. To slightly complicate matters, it's a train. He can be quite shy, and has speech disorder so struggles to communicate with other children. Today we went to the playground and another child was there we knew. DS happily played with him which I was delighted about, he is normally very reserved. But he kept referring to himself and his imaginary friend. The other kid would have no idea what he was talking about. I worry as they get older (hes already the youngest in the class) he will alienate himself.
I feel like I need to gently explain to DS that other people won't necessarily know or understand about his friend. But I don't want to discourage him from trying to play and make friends if this seemingly is a bit of a crutch for those situations. Does anyone have any tips on how to approach the subject with DS?