so far every client I have ever asked about this type of thing, they have not wanted anything from engagement on/in their wedding album. for your image, I would probably say "no" but there are some images that might work well. I just really think they should be "together" in this image for the cover.
I use te essesion photos for the albums with no problem for my clients but never
in the cover.
Well, I understand this together thing in Weddings, an international kinf of institutional rule but in the picture
I showed they are looking at each other and not oposite so no implying separation messege.
you will have to let us know what they think, I was first visualizing this where it wraps around the front and back of the book, but I am guessing you intend to have the full image on the front only which is different entirely than my first thoughts of it, even then I still think an image where they are close or touching each other might be a better choice for a wedding album cover.
awesome that you have been able to include some from engagement inside of the books, so far that hasn't happened for me and I have asked or given the option to include some if they wanted to.