If you have a dock, take the kid fishing at the end of it, just to see what exaclty is in the water. He won't have to get in the water for this one and it might put his mind at ease if he catches nothing.
Also, if you have a gradual decline, rake the leaves out of the water early spring every year. I know the dead-leaves look of the bottom of the lake isn't really appealing on my behalf
