It won't cover everything, but digging around
http://www.instructables.com/ can yield some interesting bits. For the basics of control and programming, I highly recommend
http://scratch.mit.edu/ this is software that allows you to program using visual components on the computer.
There are so many aspects to it, it is hard to point to one right place depending on what the particular appeal is. Another resource, though targeted to older kids for competitions is First Robotics.
http://www.usfirst.org/There are also the LEGO leagues (including a junior one.) I believe those revolve around LEGO Mindstorms, which is itself an awesome resource because it has the free-form experimental play that most robot kits are missing.
You make also want to check if there is a hackerspace or makerspace in your area as some of them have kid-friendly days or are involved in coaching some of the robotics competitions.
I find any of these as good of resources for a gifted kid or an adult. Maybe letting him teach and co-learn with you may be the best/easiest outcome?
p.s. Never undervalue the experience of taking apart an old printer or tape player with a screwdriver (they have technical motors and similar mechanic systems to robotics.)
