Tzeentch laughs at likely
Join Date: Dec 2009
Location: Inside my Head, Bristol, UK
BRB, p20 "Unexpected Problems" indicates that if - despite having enough movement distance to complete a charge - a unit will not fit due to the presence of other units, it is best to treat it as a failed charge. So, on a strict interpretation, you move the chargers one at a time in any order with any that cannot fit due to previous units failing.
However, all BRB rules are subject to the overarching rule that you should have fun rather than just obey the rules, the the sidebar say best thing to do not what you must do, so I suggest discussing it with your opponent before the game to reach an agreement.