Sounds like a very cool trip. My wife and I are involved with the camp ministries of Mount Hermon in the Santa Cruz mountains. They have an adventure camp called Kidder Creek, which is about 15 minutes from where you will be. I haven't been there yet, but I hear it's beautiful.
I just returned from a weekend of mountain biking at Northstar and Kirkwood in Lake Tahoe with my 15 year old son. I think he'll remember it for years to come; especially my bad crash that I still haven't recovered from - gotta remember (
BEFORE I try stupid stuff like jumping off 5' high tree stumps) that my 43 year old body doesn't bounce back from injuries the way it did when I was in my 20's.
As far as things to do and see if you're flying into Sacramento...
California State Railroad Museum. Located in old downtown, this place is a MUST SEE if you're a railroad buff, or if your just a gearhead who likes transportation stuff. I had never considered locomotives as art before visiting this museum. Virtual tour linked from this page:
http://www.sacramentocvb.org/press/things2do3.cfm?id=1707Towe Auto Museum. There's a link to a virtual tour here:
http://www.sacramentocvb.org/press/things2do3.cfm?id=665I haven't been there yet, but plan to go the next time I'm up there.
Check out this link for more things to do in and around Sacramento:
http://www.sacramentocvb.org/press/things2do.cfm Also, contact the folks from
Capitol Panteras to see if they're having any meetings or events while you're there.
And for places North of Sacramento, Lassen would definitely be interesting. You can also go by Lake Shasta. Google them for specific info on what other activities are available. My daughter just spent a week with friends house boating on Lake Shasta.
Anyway, have a great time with your son.