I’d worry that if he’s not really into math, most math camps would turn him off to math. I’d only send a kid to a math camp if they were asking to go or if I found one that really looked fun to my kid.
LEGO Mindstorms, rockets, game programming, and things like that are more reliably “fun” for a wider range of kids.
Since you are in Orange County, is this a good list of your local camps: http://www.orangecounty.net/html/edu_camps.htm? If so, and not knowing local reputations and costs, I’d look into the Explore Ocean camp, UCI Gifted Mammoth Math & Physical Science (if he qualifies), iD Tech camps (if you have money you don’t need), PlanetBravo, IncrediFlix, and Brain Builders (LEGO). But, I’d mix some of those in with about an equal number of outdoor activity camps.
Also, are 6th graders going into 7th eligible to be CITs (counselors in training) in your area? If so, see if he can CIT for something like the Discovery Cube or Camp Invention camps.