This is a real problem, but I don't think this issue is a "kids/adults" issue at all. We have no kids but also have no objection to kids activities, poolside or anywhere else--that's not the problem.
The problem is simple: VOLUME. Why on earth does the pool activity music have to be so LOUD?
At the WL we could hear it, full blast, in our room (three floors up and not particularly close to the pool) with the balcony door shut tight. There's simply no good reason for the music to be that loud, and it can't possibly be good for the kids who are inches away from the speakers. If it's loud for me, 200 feet away behind a closed door, what must it be doing to their ear drums?
"Kids" does not have to equal "ear-splittingly loud music." In fact, one could argue that for their sake, it shouldn't.
The pool music doesn't need to stop, we just wish they would turn it down to a reasonable level. It's a pool activity--as long as folks in the vicinity of the pool can hear it, that should be loud enough.