I'm interested in adding a little survival management to 'Racing to Ruin,' and crunched a few numbers on what was required in the food/water department.
Skipping the math, it comes out to about 300 pounds of food and water just to get to Kalabuto where they can presumably resupply for the second leg.
When you ran 'Racing to Ruin,' did you enforce any kind of consumables tracking? Did you assume water was freely available on the overland trip (which drops the burden down to 18 pounds of food)?
Overthinking Portion:
The Survival skill allows a character to feed the party with a DC 18(-ish) check if they cut their travel speed by half. I'm assuming this won't be on the table considering the "race" portion of the adventure.
General position on this type of thing is that if you think your players will think it is fun to break out a spreadsheet to track things down to a detailed level, then great!
Otherwise, I would tend to stick with survival and spells. If Create Food / Water isn't a party resource, then you can have fun with survival checks.
The survival DC = 10 + (2 x #PCs) to keep party fed/watered and move 1/2 overland speed.
You can make things really easy with single survival checks, thus downplaying the role of foraging during this trek. Or, you can go with more complicated checks (as I made up below). Again, I would base the decision on what your players will think is fun.
Complicated Example,
Complete pass = enough food or water found for the day. For each +5 over DC, they can also carry extra for another day. Carrying extra negates checks for those days, allowing full overland movement (but can potentially slow progress if they have too much hoarded)
Minor Fail = Did not find enough food/water. Character's take -1 as if sickened to a lesser degree.
Fail = Did not find either food or water. Character's take -1 as if sickened to a lesser degree. Make another check to see if lost.
Larger Fail = Did not neither find food nor water. Character's are as if fully sickened. Make another check to see if lost.
Serious Fail = Characters hungry, thirsty, and seriously lost. Lose one day and can try again tomorrow. May have also consumed poisonous food thinking it was safe (save vs. an appropriate poison).
Penalties are cumulative until suitable food/water consumption occurs. 3 days of no water or 8 days of no food also leads to nauseated condition. While 4 days of no water or 10 days of no food leads to death.
Spending the entire day foraging can give a +10 to survival, but no travel progress is made.
General position on this type of thing is that if you think your players will think it is fun to break out a spreadsheet to track things down to a detailed level, then great!
I don't know that it would call for a spreadsheet, just a "day 2, subtract a pound of food."
It seems to me like any expedition intended to last 2 months should have some aspect of survival to it. I'm mostly inspired by 'Jade Regent' which embraced the nature of a cross-country trek.