I'm sorry if this post is not very helpful but I (and most members on my team for that matter) learned how to build these robots by doing just that, building the robots. There are no books or manuals on how to do it, you just have to pick up tidbits of information from other people, you school work, and the internet.
Sure some engineering textbooks are great. The same goes for a physics background. However, there is no way to learn better than working alongside engineers your rookie year with them letting you do most of the work (including design) but guiding you through it. Our team works by letting the kids do everything but if the adults catch a blaring flaw in the design or we don't know how to do something, they help.
Heck, our rookie year, we had a plywood box with two motors and two drive wheels (roller casters in the front).
One resource I would have them look at is the numerous powerpoints.
http://mnfirstregional.org/MNEvents/MNSplash.html and
http://mnfirstregional.org/MNEvents/mentorinfo.html are some links to power points. They provide the absolute basics you need to know.
I know that I learned a lot of stuff just by having a CD account and just posting and reading threads in here.
-Vivek