Hm. Possibly, though to be perfectly honest I'd be surprised if we ended up filling more than a couple. Plus didn't Nirur say Chaun's three gold slots were loot slots? We've got 1.5 loot slots on any mission he's on anyway.
Speaking of which, I think our first mission should be all four of our level 1s. This might be a bit risky, but with scaling challenges hopefully nothing they can't handle. If successful, it'll also make everyone but our dwarf level 2, which is a great place to start, I'd say.
The other downside, of course, is that they'll be both squishy and only really able to use 2 battles for leveling purposes before returning. We'll be relying on checkpoints, so obviously that might not happen anyway, but it will probably tend to push the mission towards brief and therefore not tremendously profitable.
Finally, I still want to conserve gold. The 15g for 50 rations thing sounds like a good deal to me, since that should last us through five dungeons. We'll need 10g to operate the gate. That leaves 12g in normal guild funds, which we'd want to save in case we make less than 10g from our first run, and 25g of Chauner's, which we might still want to hold onto in case two missions go sour.
Overall, I'm fine with buying one or two bags, especially if someone specifically wants them, but I don't think a full set is a good idea, especially since a bag 50% larger would presumably only cost twice as much. If we needed that many slots, we'd probably want to go for the upgrade.