Ah, Dirk, always with the alternatives!!
This is how I do it, and how I can pretend my kids aren't peeing in my pool. Pee Pot!!
$12 Mexican planter from Lowes, about 14" diameter or so, filled with dirt, placed around a corner from the pool, in a dirt patch right next to a concrete slab. My 6 and 9 year olds get a kick out of using it. And take all their friends back there with them. Probably some Ghostbusters crossing of the streams going on, who knows. All I know is that boys are nasty and find anything potty-related to be a hoot, so while they might still be going in my pool, I know they are at least doing so less than they would have otherwise. It also keeps 'em from slip-sliding on my travertine tile inside the house, to reach the closest bathroom, which is down-right deadly for wet feet.
I got the three-year-old girl to squat over it the other day. Wishful thinking, she cried the whole time. So not much hope there.
Winter rains clean it out. Might even keep the deer out of my garden!
OMG, I love this! Honestly, it doesn't smell??