More than likely the pump was cycling on and off the whole time you were filling the kid pool. This will stir up the well and make it cloudy. Usually you have to run it wide open for quite a while to clear up a dirty well. Make sure you have enough hoses runing at the same time to keep the pump from cycling off.
Or it could be the opposite. If you have a weak producing well, then running it hard in the kid pool could also make it cloudy. I think you would have pumped the well dry and you would have known if it is a weak well. So I am guessing the first idea I mentioned is what you need to do.