I think the quilted cover of the album would be wonderful.
Something that I have seen done that fits with your plans is to give family members (friends too, if you wish) a page for the photo album to write some memories to give to them. An adult child may write a letter. Another an array of photos. The younger GGGrands may draw a picture. Someone might write a poem. Etc, Etc. It's amazing the creativity that comes out, as each gets going on it ... and for your parents it's really a grand gift, as it gives them something to enjoy for many hours and days after the event, when not so many people are around them.
Depending on how large your event is going to be, you could distribute the pages to your other guests to do before they come. Or ask them to jot down some of their memories and bring photos, then you can add to the book after the event.
Happy Anniversary to your folks!