A natural way to prevent mosquitoes in a kiddie pool?

Is there something natural and not harmful to kids that we can put in the kiddie pool to prevent mosquitoes and other bugs from using it as a breeding ground? Like lavender oil or something like that? It's just an inflatable kiddie pool, about 4 x 6 feet in size. We're hoping to not have to empty it out each time they use it so the sun can warm up the water.