Milan-Chievo? Bring pillows.
First of all, he's a Juve fan. Milan may pack in the stadium more, and the stadium may be clerly superior to the delle Alpi, but Chievo? You're going to take your son to see Flying Donkeys? And with a home Milan squad that already feels the Scudetto is out of reach and thus the Serie A season is just a matter of biding time between Champions League matches?
Or, in contrast, you take him to Torino. He's a big Juve fan, and Torino is a wonderful and too often overlooked city. As a juventino, going to Torino and the delle Alpi is like a religious pilgrimmage (I know this first hand). And every time he watches a Juve match at home on TV henceforth, he'll be able to reference back to the atmosphere at the delle Alpi as a juventino -- and not some milanista interloper.
Then add to that Fiorentina... one of Juve's greatest rivals of all-time. You'd get to see Luca Toni before WC 2006. You'll get to see the ultras incited to mock Fiorentina mercilessly. Afterall, remember the Coppa Italia match at the Franchi earlier in the season where tear gas was released and the game was suspended for 45 minutes? Not that it's going to happen here, but that shows you the level of spirited rivalry to expect on Juve's home turf against Fiorentina.
But do not mistake me...my comments here aren't intended to be snide or sarcastic in relation to you at all (thanks for posting!). I am just trying to add a little "juice" to the discussion in why I think it's a no brainer to pass on the Meazza and head for the delle Alpi instead. You'll be glad you did.