Murder Mystery Website Development

I had a designer and a developer helping me with my website, but, unfortunately, the developer was unable to finish the project. At this point, it is 90% complete. I just need help finishing it. The pitch: I need a platform where customers can purchase a game and, during the purchase process, input multiple email addresses to receive different files. The crucial part is that the system must automatically send a unique character role to each specified email address for each player. My developer was able to set up a complex backend system to do this, but he could not replicate it easily so that I could add new games myself. Thus, I only have one playable game--when I want the option to add unlimited games with ease (myself) and grow my business. My last developer has instructions/notes about what he did, but I am very open to alternative solutions that achieve the same goal of secure, individualized role distribution to multiple players with a single purchase. I'd be grateful to hear thoughts and whether this is a task that can be accomplished.