If you need to adjust the saturation of each image individually, there is really no way to automate it. To apply the same saturation, you can do something like this, but it's pretty slow.
saturation = 2;
ExampleData({"TestImage", #}) & /@ {"Apples", "Flower", "House"} //
ColorConvert(#, "HSB") & //
Map(ImageApply(({#((1)), saturation #((2)), #((3))} &), #) &)