Honestly sometimes, that's all I do. In a pinch, not even that. I have a gut feeling that you are about right.I use between 3-6 hours of fresh air/sunlight per 5 gallons of water. Chlorine naturally evaporates from water (this is why it needs to be continually added to swimming pools), fill up your buckets and let them sit for half a day before watering the girls, almost all of the chlorine should be gone by then.
I also let the water sit even a little longer before brewing compost tea with it because I don't want any leftover trace chlorine to damage/kill the beneficial bacteria.
However, not only are there several variables involved, but I also have no way of knowing for sure. Therefore I think a little redundancy may be prudent. I.E. A little organic material, maybe a little dried orange peel for a little citric acid.