They are the attackers. The town is a pirate town, and they must try to assault it and "bring them to justice" somehow. They're a mix of LG (monk/rogue), NG (favored soul), CG (wizard/rogue), and two CN characters (druid and barbarian). They also have eight second level soldiers with them (fighters and two halfling rangers).
They just discovered that what they thought was a pirate camp turned out to be a whole village of pirates, with 30-some pirates and just as many slaves, women, and children.
The village is hidden in a swamp. It has two lookout towers and a clearing around it. There's a dock and warehouses and several group barracks and tents. The pirate leaders are a fighter and a wizard - so not stupid. They are evil, so evil options (use the non-combatants as hostages perhaps?) are definitely on the table.
They're a long walk to civilization; but the druid can shift and fly to the city in a day or so.
The PCs' plan is to pick them off like guerillas, with ambushes etc. instead of taking them all on (though they could actually do that). What would YOU do if you were the pirate leaders, if some group started ambushing your patrols and striking into your town?