You haven't got a hotel - try Hôtel de Verneuil in the 7th, I always recommend it, I love it.
Take him to the Café de Flore on boulevard Saint-Germain for the history and the celeb spotting.
What kind of food do you/he like? Italian, Lebanese, French, Japanese...? My 12 year old stepson loves Amici Miei (pizza), Noura (Lebanese), Little Italy (pasta), Café Marly (at Louvre) and Georges (at Centre Pompidou) for French/all day. Tell me what sounds right and I'll give you details/more addresses.
Things to do - what's he interested in? How long have you got?