I would ask your wife how she intends to use the sundeck. So it's going to be 4' wide, but how deep? Meaning how much water over it? I would be thinking i would want the first step to be the sundeck with 4-6" of water over it.
So i have liner over steps in my pool, installed last year. My first step is 3' wide with 4-5" of water over it. It's great for the kids, and adults to sit on. We don't use chairs in the pool, but it would obviously be too short for reclining chairs, as would yours. There will be foam over your steps, I would hesitate to put chairs on the shelf, unless the chairs legs where.......well i just wouldn't do it for fear of a puncture, but the stuff is pretty tough, but the foam underneath it on the steps makes me wonder.
I would ask your pool builder to let you see a liner over steps build he's done. Maybe he's already done that for you. I would just want some assurance that the liner over steps part looks good. Mine is functionally fine, but the ascetics is lacking. I think mine was miss measured by like 1", because there is just a tiny bit of extra material at the end of each step.
Here's a blurry underwater picture of the end of one of my steps.
Another question, Given how thick your chosen border is, how will it interact with first step?
Finally, i highly suggest you get the tread tex version of your liner for the steps, sun shelf. Ask your builder about it, there are only 4 patterns i think, and i choose my liner based on the 4 tread text versions. It's non-slip, and has kept us from busting our butts. The rest of our liner is supper slick. Just to be clear in the above picture the step surface and wall surface have different textures (barley noticeable, but non-slip works).
Make sure your builder gives you the scraps for future repairs. And a piece (sample) of the border.
Make sure your bottom is perfectly smooth prior to liner installation....you don't want to see foot prints at night
You can see ridge on last step here
