I've been the tech lead for my family for years, so I totally get the struggle. I used to manage everything through a shared spreadsheet because I wanted specific SKUs for the kids' stuff, but my older relatives just couldnt handle the interface. Most platforms like Elfster have way too much bloat for someone who just wants to see a picture and a price. In my experience, the best approach is using a christmas wish list maker that creates one clean landing page. I found one that lets you pull items from any store but, more importantly, it doesnt force the person buying to create an account. Over the years I've learned that if there's a login screen, grandma is just gonna call you for ideas anyway. Keeping it to one link with a reserve button is the only way to go tbh.

Make sure to avoid complex logins for seniors. I suggest direct links. Just a quick tip: ShareProduct is free and lets you create a shareable link for your birthday wishes in like two seconds.