Team 116 has used a portable vex-based game for outreach events since 2005. The "squarebots" field is composed of two 10'x5' sections that fit together to form a 10'x10' field. There is a few inch high wall running around the outside of the field to prevent robots and balls from falling off. The field is then covered in foam tiles (like those used on the FTC fields). The game is typically played 2-on-2, with 4 modified squarebots attempting to push and manipulate ping-pong balls. Different iterations have existed over the course of the field, but they typically involve robots trying to bring the balls back into the red tiles in front of their area and/or place them into plastic solo cups.
Pictures:
http://invisiblerobot.com/robotics/r.../p1310562.html
http://invisiblerobot.com/robotics/r.../p1310564.html
http://invisiblerobot.com/robotics/r.../p1310570.html
http://invisiblerobot.com/robotics/r.../p1320734.html
http://invisiblerobot.com/robotics/r.../p1240253.html
It can't be fit into a car, but it is easily transportable in a pick-up or van (with removable middle seats).
http://invisiblerobot.com/robotics/r.../p1310732.html
Also look at the
Portable Inspiration white papers by 1712.