I just wanted to give a quick update.
This morning he sounded out 'car' his first word! We have been taking things slow and following his lead as suggested. Lots of reading including the occasional BOB book, Starfall, letter magnets, Super Why and the Magna Doodle, which is what we were doing when he 'read' today.
He is also counting objects like toys up to 5. I didn't realize this was a big until my friend with an early childhood degree about fell over when she saw him do it. Of course she works with disadvantaged 4 year olds so her frame of reference may be a bit off.
But once again, I just wanted to say thank you to you all for your excellent advice and support.