That already is a handy script
(although for performance's sake it's not necessary to declare so many variables).
If your tank group's leader tank is MyTank, add the following to your radio trigger on act field:
MyTank moveTo [(position player select 0)+100*sin(direction player), (position player select 1)+100*cos(direction player)]
That makes them drive to 100 meters in front of the player (or more accurately where player's chest is pointing).
Of course you need to account the horrible driving capabilities of the AI and they might not ever get there..