i have the nieces & nephews over all the time. They work hard. Kitty litter, recycling, painting walls, scrubbing the place... work their asses off for hours... then we go to a water park. "hard work pays off!" they all say. It's completely voluntary - if they agree to 2 hours of work, they get 6 hours of water park. Or, they can play video games/tv and they go home while we go to the water park (or mall, etc)
I see nothing wrong with kids cleaning up after themselves. Urine is pretty gross, but already, that classroom should be a place where EVERY kid owns the cleaning, daily. Stop 3x a day and clean that classroom. Everyone grabs 3 things, and the place is spotless in 30 seconds, it's easy.
instill that pride, and kids aren't pissing all over like animals. They WANT a clean potty in there. cause they own it.