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)
I wasn't suggesting they code their own site up. I only mentioned my involvement to suggest I had some familiarity.
I've been at these events where attendees are actively asking people for assistance. My nightmare fuel was people actively seeking out the photog during the event for that assistance. Asking the photog to be tech support for this is not something that should be on their list of duties. The photog could possibly provide suggestions for the couple to use, and put the burden on them.