I wouldn't get shell dwellers with anything less than a 10 gallon, and especially not with other bottom dwellers. They're very territorial and with such a small footprint in a 5 gallon, they will attack the cories.
Oh I meant that I was thinking about the shell dwellers instead of the cories (I wouldn't put them together), but if they need a larger home anyway, then it's not an issue. I'll stick with the cories.