[X] With the left-flank anchored in the lake, and move forward with the right to immediately occupy the hills in the early hours before dawn/as the fight starts, and then rain down destruction with the cannons, hopefully.
[X] Massing around your right (their left) in order to force the enemy to overextend there, hitting them on occasion/harassing them on that side, but allowing them to anchor on their own lake decently well.
[X] Move to spread out once one reaches the hill, forcing him to have to thin his forces if he doesn't want to be flanked (would work best with using Rassit on your right). If he spreads himself thin, he'll be weak everywhere, and if not, an actual flanking manuever with a detachment of the troops becomes possible, easily, with all of the advantages it would carry.
[X] A left-right strike. Strike the left (their right) as if trying to go around the lake and hit them at the same time, and then hit the right hard, with as much force as possible, and then see what they do. If Jinhai weakens his left upon thinking that it's a feint… make it not a feint. Move in with what they have and hammer both sides. If he keeps his forces committed, shatter his right and roll him up.
[X] Entrench hard and use the cannons and superiority to hold him to his losses, while the Rassit and other units pick away at him until his plan is evident and can be countered.