I think that kids have as much a right as adults to use the main pool, and if they don't want to swim lengths in the general swim area, well, that's fair enough; it's not just for us adults. If there are multiple lanes roped off then one is generally labelled as the slow lane, so surely that's the place to swim if you aren't a confident swimmer? It's the one by the side whenever I've been, so if you run out steam half way along you can stop grab the edge. Have to confess I've never been there late afternoon so have never seen it as described then. Later in the evening it tends to be pretty much all adults doing lengths when it's not reserved for lessons/clubs.
It does get frustrating when it's too busy, but not really sure what more you can do about that; it's great that people are using it and we just have to share, although I admit I got frustrated weaving in and out of people last week when there were no lanes for non-club people.

As for cleaning, yes they could do more, but really why do some people have to be so disgusting? The shoe covers seem to have disappeared too.