That sounds pretty good to me. We just finished filling up our new pool with water today. It's about 40x18 of swimming area with spa on the rear center and a fairly large ledge on the front center. Our pool depth is 4 feet to about 6 1/2 - 7 feet. Our last pool was 3 1/2 - 6 but our kids are older (10 & 13) now so went a little deeper. I'd say ours slopes off gently from 4 feet in depth around 15 feet from the edge and we are very happy with the slope they did. We are also absolutely thrilled with the way our entire pool turned out. Good luck.

We built a large shallow end for volleyball and play in our pool that is 3.6 to 4 to 3.6 and it is perfect. It was great when our kids were younger for play and it is perfect now that they are over 6 ft when they play volleyball or just hang out. .
Our pool has a separate diving area that is 9 ft deep. Because we wanted both features, the pool is long (to allow for torpedoing from a dive) then the wide shallow area. However, the drop off between the two areas is very steep. It would have taken a lot more room to have made it more gradual.
This shot is not the best angle to show the length.
We also put umbrella holes in the deck to hold the volleyball net across the pool. Make sure yours come with caps. We had to retrofit ours and they stick up, which is bad when you stub a toe on it.