Used to do this with instant prints. Also have helped a friend do tintype portraits.

The cool factor will be quickly forgotten once you tell them "I'll send you a print in a few days." Sorry but I think you'll get exactly 0 customers with that approach. Most folks don't give strangers money and hope to get the product later.

Besides which, for 95% of people there, they want a cell phone pic to post on social media. Not a print to put on the wall. A small instant print of decent size was attractive back a few years ago (I was using 3x4 Fuji 100C and 3000B instant films), but these days with Fuji having sold millions and millions of Instax cameras, many of your potential customers will have their own way of doing it if they want small scrapbook photos.

And don't forget the regulatory stuff as mentioned earlier.

I could be wrong but I think the idea as presented will be a really tough sell.