I agree with Tad; the mountains are an ideal location for an end game.
You could have the final challenge be the guest appearance of the Donner party, either as crazy cannibals, zombie/vampire monstrosities, or a happy combination of the two.
Tad, that sounds like an awesome variant of Werewolf/Mafia/whatever the kids call it these days. Sounds really cool.
I might suggest giving players handouts with some information that the other players don't have and let them have fun forming deals and accusing each other.
I would also involve The King in Yellow, but that is just me...