If you're team is planning to use or considering using WPILibJ, there is a coding game called robocode at
http://robocode.sourceforge.net/
It actually uses templates (Simple and Iterative robots) very similar to the WPI Libraries, and there robots and standardized and virtual - and if you have 4 students you could have them program bots to compete against each other (the robots are basically mini tanks) without having to build a kit-bot or something for them to play with.