Page 91 seems to set out how to resolve your dilemma in impact. right hand column top of the page. Says turn any bases required to turn to face a flank or rear charge and proceed as follows:........ This includes bases contacted on their flank or rear which were unable to turn because they are already engaged to their front.
So yes I guess it depends on who charges first as to which way the chariot will have to turn. Moving players choice so I guess the LH charges will decide how the chariot turns.
Further down same page it says if both side have an equal number of bases eligible to fight, all of them fight. ..... IF the number of eligible bases is unequal both sides fight with the lower number of bases. The side with the higher number of bases chooses which of his bases will not fight. His choice must leave every eligible enemy base paired off against one of his.
So for impact looks like you get 2 dice for the knights and 1 die for the LH. One of the LH units does not get to fight in impact since its 3 enemy to 2 chariots. I think the reference to dishing out combat dice among all engaged enemies only applies to melee. So its ++ for the chargers, -- for the chariots. I almost think your opponent would have been better staying with a head on charge and go for dice with the knights and next turn bring in the lights, or held back a LH for a turn to get one more ++/-- impact on you on their next turn.
In my originial post I thought we were talking melee not charges
