Selection of proofs by B&G

I have two weddings ahead and am trying to determine a few things for my whole workflow.

In my first two albums, it was me the one who made the picture selection, but then I learned that photographers make proofs (around 500, if I am not wrong) so that the couple can make the selection. I can see the point in this: a more successful album with their likes (after all, it is their album), and less work for the photographer (I spent a lot of time deciding which ones to include).

Here are my questions:

• Say I am asked a Flush Mount album, 10x15 landscape, with 20 pages/sides. How many pictures do I tell the couple to select?
  
• Do I have to view this selection as the law, or just as a guideline?
  
• Can I add my favourites?
  
• Do I ask the couple to select which ones are in B&W, sepia, etc., or this is my option?

I usually do it this way:
- do the design with the photos i like
- let them see it
- make any (reasonable) changes they ask for
- let them see it (and repeat if necessary)
- once everything is good and happy, order it

This keeps things on my timeline for the most part, no waiting for them to choose shots. They can still change or add, but it gets the most stuff out of the way. Generally people are a little overwhelmed by the task of picking a selection of photos.

I have three options for image selection:
1) My choice (no-one takes me up on this)
2) Tell me your favorite 20 images (some people do this)
3) Pick 2 images per page, and let me fill it out with extra images as necessary (most people do this)

I find 2.5 images per page on average works well, for a matted album (I do 90% matted), a bit more for pagemount albums.