Your pool looks like it's going to be fantastic! Love the deep end, diving board, volleyball net and basketball hoop planning. We have those too, and people enjoy the pool more and use it more with various things to do. And at bbqs, it means everyone is in the pool for most of the party - kids and adults
A few thoughts:
For me, 3'4" is too shallow for the shallow end. Kids grow fast, so don't plan around their height now. I would strongly suggest 4' water depth for shallow end. Also make sure you are super clear with your builder on the water depth you want on your sunshelf. We have 9", which is perfect for us, but others prefer deeper so you are in the water more if on a ledge lounger. And make sure you and your contract specify "water depth" clearly so that they don't build those heights to the top of your coping or something, giving you 6" less water depth.
We have a volleyball net and love it, and it's used all the time! In a perfect world, you would have 10' on each side of the net for playing for a total of 20' flat, shallow end. But that's not always possible (I don't have that either)! If you did change the shallow end water depth to 4', then you would only need 12' for the slope from deep to shallow (3 feet horizontal for each 1 foot vertical is I think the standard rule) so you could gain a couple of feet back as shallow end by taking up less length on the sloped section.
6 feet is ok but might be just a little tight on the sunshelf. I agree with Aquaholics on 7 feet. I have close to 9 feet on mine, and it's more than necessary for sure. If I were ever to build a pool again, I think I would go 7 or maybe maximum 8 feet. 20 feet wide is huge for the sunshelf, so I would think again about recessing the steps into the shelf - you have plenty of room. Do you need steps on both sides? Of course it's nice to have them like you do so people can sit all across the pool at different depths - I really like that alot! But for me, the trade off of a bit more shallow end would be worth it. If you end up changing your mind on the auto cover, you could also have a bumpout sunshelf rather than having it be within the main pool rectangle. But with an autocover (which is a great thing to have!) , that is not an option.
Best of luck with your house and pool build!