[X] Kiralo could slow down his movements, to try to angle the battlefield as a lake-filled region that also has a number of small hills that might be useful for placing cannons on, depending on the landscape. He can anchor his forces against a lake if need be. It'd involve waiting a little, but he can shift to keep it from being easy for Jinhai to get past him...and if he does, then that's Jinhai's lost.
[X] Speed up a little. There is some good, dry farmland in an area with quite a few small towns, villages, and castles whose walls could make a good place to put cannons if the fight shifts the right way, and if it doesn't, then there's still good ground for deploying the Rassit, because the flanks will be wide open on plains like that.