REFUGEVILLE

All of those except one, with a bit of hurry none of these action are mutualy exclusive.

Except the poisoning the river thing (I mean forget the fishes, it's also your source of potable water, you REALLY don't want to poison that).
Although I have to question just how potent that poison is if a single spider can poison a whole freaking river and all the fishes in it, seriously just seeing Kori should make those mlercenaries soil their loinclothes...

But yeah put mercs in the front. One villager sacrifice some rabit meat, the other carve some lances as fast as they can and have Kori poison the tip (or poison a bucket of water and just dip the lances in)
When the bad guy come, throw the lances and then rush into the house to defend from there while the mercs hack at the rest.

Of course you could just try to talk the mercenaries out of attacking you, mercenaries are kind of open to beoing paid off, it's kinda why they are mercenaries in the first place but eh, i doubt you have anything they'd be interested in and they could repport your positiuon to the Signet so...