Excellent points! I suspect OP wants to have the whole caravan in order to not make this a survival/resource management focused campaign so I'll offer a way to do so that would make sense since, as you describe, they shouldn't be bringing a huge trade caravan into the unknown: big old disaster. Some terrible, world changing thing happens and the only way to go is forward, into the now unknown region.
I think letting them be a shot force works just fine but if OP has some crafting or job based thing baked in an act of God could let them keep that and verisimilitude.
I've been meaning to make a statement block and encounter for this forever. I should really get around to it.