Hi Barbara,

Great question from your son. I remember going through the same phase.

You might look into Lucid Dreaming.

In addition, the Australian Abos have a lot of wonderful legends around it that your son would love.

http://en.wikipedia.org/wiki/Lucid_dream

http://en.wikipedia.org/wiki/Dreamtime

And he will love this book.

http://en.wikipedia.org/wiki/Jonathan_Livingston_Seagull