Exactly, the wedding photographer ought to set you up with a "white label" version of the above web sites or just pick one out and set it up for you. I wouldn't expect them to code it up any more than I'd expect them to build a custom camera. On the other hand it ought to be part of the service because it is something they can do in a few minutes without thinking about it while the organizers could struggle with it.

(Kinda funny that my photographer friends online tend to automatically discount any software I've developed myself for image processing; a lot of them still think sRGB is the "standard" color space in 2023 despite mobile devices mostly being Display P3 for some time)