Okay, if Elven Cavalry 2 does chase after the Disengage, and Elv Cav 1 is the one that eats the Ready Fire from the Horse Artillery, and it is routed, then our Hobgoblins will be in range for a charge on Cav 2 (range of 3, just enough to get that charge going) at the same time as we just plain regular fire at Cav 2 with the Artillery.
I think? If instead both enemy Cavalry are routed we'd just do a more generalized advance as much as we're able to get rid of the Halfling militia while they're still figuring out what's what.