I think this is my favourite idea so far!
To be fair, that Tiana has a thriving business is not unreasonable as part of the backstory. What we know of this backstory, though, does seem very much like the kind of over-complicated backstory that Disney specialises in these days: Tiana's restaurant was going so well that she decided to expand her business to a food processing company but, don't worry, it's a good one that is employee owned. As part of this effort to expand her business and brand, she also bought a salt mine. So, that's why you're now riding through a salt mine on the way to Tiana's party.
It just seems a bit... forced.