Photos w/ Santa - Suggestions for Organizing Customers

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I have been asked to shoot fundraising pictures of people and their pets with Santa.
Any recommendations or online guides on how to efficiently track customers and their photos associated with them for later download.

Here is the high-level process in mind head.

1) The customer donates $X for a photo with Santa. In return, they are given a unique download URL piece of paper to retrieve their pictures later
2) Photos are taken with family X, and the photo numbers are #5 and #7 for example
3) Photos are processed and uploaded
4) Family goes to URL download their two photos

Lather rinse and repeat steps 2-4 for the other customers.

Is their software, howtos, etc. on how best to process, track and offer downloads to customers like this?

Thanks in advance,