Just my .02, with 9 kids i would be trying for as many gallons that i could fit in my backyard. You'll have an 11 person party every weekend before inviting anybody else over. I get the whole sunshelf idea. I do. But its for relaxing at a resort on vacation. Or having a slice of that in your own backyard. For people who have peace and quiet and can do that. With 9 kids you need as much swimming space as you can so that they all can do as they wish and not have to take turns here, there and on the sunshelf.
So I have never owned a pool. It will be 16 x 36 and then a 16 x 8 sunshelf. My oldest child is only 15 years old but I’m thinking we might have lots of grandchildren.? I thought a sunshelf would be fun for the grandkids. I think I also want it for myself.