I've lived in this area since the 1950s and during those years spent many a day swimming at local swimming pools.
I know we have not been successful in efforts to build a new pool and that many families travel to Milton-Freewater or Pendleton to swim and cool off. I think that is great for those families and those towns, but we have a lot of kids who can't do that.
A few years ago, I lived in Portland and my grandkids would come to spend some visiting time during the summer. Their favorite activity of any of the things we did together was to go play in the Salmon Street Fountain.
This is a fountain formed by different spouts in a big cement circle flat on the ground. The water comes out in a spray, or a waterfall or it shoots straight up.
It alternates between certain spouts and the kids don't really know where it will go next. They have placed some benches around the edge so parents, etc., can keep an eye on things. It appears to entertain a ton of people of any age from toddlers to oldsters.
I don't know if this is a new idea for Walla Walla or one that has been discarded but it seems worth considering and would appear to me to be much cheaper than building, staffing and maintaining a pool. And ... it would be a lot of cool fun!