Sue, I think that the best idea is to get the house cool with moderate humidity levels and the way you get there is with an air conditioner. Trying to dampproof everything in your house is the road to disaster.
We had those lovely swamp coolers when I was in the Army. The fan made a nice breeze but with the windows open in Oklahoma, the little humidity it added (along with the little cooling) was hardly noticeable. But it did give us an excuse to go find an air conditioned bar, not that we needed an excuse.
You would have a lot different situation if you are in a climate that is already humid and you keep the windows closed to keep the cool and humidity inside. Check out air conditioners, even if it is just for a room or 2. You will see that they condense the humidity so it doesn't get inside your house. This is what you and your floors want.