Welcome to the frustrating and rewarding world of Aqueduct fishing. Me and my sons, who are 5 and 6 fish the duct probably 3 to 4 times a week here in Palmdale, it's only a 10 minute drive for us.
If you live here in the area, the cheapest place for chicken livers is Food 4 Less at AVE. S and 25th east, about 1/2 the price as other stores, and they come in quart containers insead of the little pint sized ones.
We consistantly score well on the cats and stripers here. Livers are my bait of choice, and like marcsee said, before the sun is strong on the water, either early AM or at dusk and later.
When the wind is howlin as usual around here, I fish up to a 3 oz. sliding sinker with a 2 foot leader. My email address is in my members profile, shoot me a line and I'll give you a couple spots where you and your sons can score some fish, I know how hard it is to keep them interested when nothing is biting.