Starting in the next few weeks, I'm going to be running a long-term duet campaign with my partner, set in my homebrew world in the post-apocalyptic conditions that follow from an alien invasion. The first leg of that campaign is going to be sandboxy survival play, with the one PC acting as the de facto leader and guardian of a group of about 20-30 people (mostly commoners, one adept, a few 1st-level PC classes).

The PC is starting at 2nd level and is a barbarian/oracle gestalt. No ranks in Survival, currently, but I've talked to my partner about how that could be an issue; they're gonna add ranks on level up (or with retraining if that takes too long), and treat the rough period before that as a character building thing.

So, any tips for how I, as DM, should be running a survivalist sandbox? Anyone who's run this kind of thing before? I've already cobbled together random encounter tables for the major areas/directions they could travel and a custom random weather table (magic has messed up the weather patterns in the region, and it's a cold tundra so not really covered in the default table anyway).