Nicely done!
A simple pre-programmed backwards motion (with each robot accounting for it''s appropriate shift on CoG), when properly calibrated, could be run by many roots on an alliance and everything would work perfect. If only one robot was driving, you would have to compensate for the extra weight of the other robots, but it shouldn't be all that bad. Maybe something other than a pre-set bakwards motion could account for different distributions of weight.
Normally I would say humans should be able to do this better, but that program is beautiful
.