You're going to lose at least 1/2 of your 40' length to keep the appropriate slope for a diving board. One thing you might do is have the pool widen at the transition so the shallow end has more width & play area than the deep end.

Another thing you might consider is using a jump rock instead of a diving board. The slope can be much shorter & steeper if you dont use a diving board, and that will gain you several feet more in the shallow end.

You'll lose 24'11" regardless of a board or a rock... (diving code is diving code) over 6' in dpeth... if you truly want a large shallow end make the pool as large as the budget will allow... also consider a wide freeform.... my 800 sq ft FF has a shallow end 28 ft wide.... the deep end only needs to be as wide as the diving template...

While our shape is not very innovative (it looks like a boot),
it takes care of our needs very nicely. I can't put my hands on the plans at the moment but I'll try to recall and attach some pics.
I think the total length on the long side (of the grotto) is 36.6 feet.
The total length of the shallow end is 27-28 feet. I do not recall how wide the shallow end is, but it has been more than adequate.

The depth is 8-9 feet (I think it is deeper but cant remember why)the amount of footage for torpedo-ing (?) is more than required (I think 2 feet) because the slope from shallow to deep is sharp.

Our shallow is 3'x 3.6 x 3. Our 15 yr old is 6 ft already and the youngest is 5.2. The depth is perfect for all to enjoy and not feel "out of the water" or "over their heads".

Thanks for the help. I think we decided on a depth of 9ft and we are going to make the pool about 43 ft long. I am going to upload our plans shortly. Trying to figure out how to do that.

That was exactly my concern as well. We went with a lazy-L shape and it has worked out perfectly!! We had about 25 people in it one day this summer and the divers did not interfere with the litte ones in the shallow end at all.