There's a lot of factors here. >_< But I think I've got my recommendation.
We take all of them except the conscripts. The Crusaders and Archers have the most significant ranged weaponry, which is what will make the most of this ambush as it's designed to unload on them while they're slowed down and trying to cross. Sir Reginald, the Soldiers, and R3N-L3 would be best for holding the front line and keeping them locked down at the river for as long as possible. They have high defense, which is what will be needed there.
As for the conscripts, they should head back to the village and prepare defenses. With so many of them, they bear the largest risk of exposing our ambush early. The smaller our forces, the less likely the raiders will see this coming. Their ranged weaponry isn't all that impressive, and they're going to be squishy on the front line. The best thing for them to do is to prepare the town while we buy them time.
A much bigger question I have is where should Lauretta be? Her spell, Shield of Righteousness, will be a massive defensive benefit to the troops she is placed with. She has a bow, so she could be with the archers and crusaders. They would be even more protected from ranged fire and unleashing as much as possible. They should already have some cover though. Alternatively, she could be on the frontline with Sir Reginald, R3N-L3, and the Soldiers. This would make sure we hold for as long as possible.
Tzal and Wolfram are flex units who can go wherever they like, really.