Is there enough to do at the two Universal parks in order to get a 14 day ticket to park?
Absolutely not. At least, not for me. I've been to Universal once, in January 2011. We had two days there, in addition to a several days at WDW. Now, granted, I was by myself for most of the time and the only thing that interested me was the Wizarding World of Harry Potter (which, don't be misled, is merely a small section of Islands of Adventures. Not that it isn't AWESOME.) and the rollar coasters. I finished everything I cared to do in the first day and spend the second day wandering Hogsmead and Hogwarts Castle.
For me, a single day was more than enough time to get everything done. For a family with children? Maybe 3-5 days would suffice? A week, at the most, if you're really taking your time. But not two weeks. Again, however, I am a 23 year old with an interest in Harry Potter and rollar coasters who went by herself for most of the trip.
As a side note: The Wizarding World of Harry Potter is worth the trip to Universal alone. I'm sure your son will love it! It is paradise for a fan of the books. Make sure to try the butterbeer!
Edit: Oooh, I was thinking that it was like...individual day tickets. Not a package deal. That changes things! I stand by the idea that it won't take more than a few days to see everything. But if you'd like to see other parks or have other activities planned, it's not a bad idea to have the flexibility to come back anytime within those 14 days.