We just returned from that same itinerary, we were onboard for Halloween week. The Vision class ships in general have smaller youth facilities then the Radiance or Voyager class of ships, and consequently there are fewer things available for the kids.
On our sailing there wasn't a single teen in the teen program or area. There honestly didn't appear to be a teen over 13 onboard. I think this was because of the time of year, however February may see more teenagers onboard.
There is a teen area onboard, I have a few photos of the space in my www.mycruiseplanner.info/PhotoGallery
photo gallery. What activities are available for your son will probably be strongly dependent on just how many teens are onboard for your sailing.
That being said, with the Vision of the Seas being a smaller ship, I think you could comfortable give your son quite a bit of independence while you're onboard. Especially since you'll have three days at sea.
We'll actually be back onboard Vision of the Seas for the repositioning to Vancouver for the start of the Alaska season this spring.