I don't know how do-able this is, but is it possible for you to get a photo of yourself (you'd probably need a fairly big photo) that you could stick to the backseat of the car (or perhaps stick to the inside of the window or have dangling from the thingo above the window), so that he can see it whilst he is still in the rear-facing position? That way he's getting to 'see' you, just in photo form?!?!