We also are looking into ebb and flow. Most of what I find is the large rez is kept outside the room. It seems in an e&b system a large body of water stay fairly cool at room temps if no heat source like lights are present. 68 degrees it best for oxy in the water but again the way these sytems work a little higher temp is ok. Your plants do not sit in water all the time like DWC so it doesn't mean as much at the buckets but you need it cool to help keep algea and cyanobacteria blooms to a minimum.
your temp in the control rez is no problem as the water is quickly divided between all your buckets during the EBB and cooler waters mix with it. Think about your hydroton in the bucket at room temp with the lights on. Must be warm. Then mix cool water, now you got luke warm ? I would like to know what the water temp is at the bucket at the moment it reaches full ?

I like this system because moving water has less problems.