Ah, right, I forgot about seeing the meter in your photos. Your temp range is real nice, especially since you don't have to do much. I've had to invest in heat lamps to get mine into those ranges.
If you're worried about humidity later in the grow, think about an extraction/exhaust fan. At the moment, I run mine just five minutes every two hours during lights on. But when that sucker runs, my temp immediately drops 5 degrees celsius and my humidity drops about 14 percentage points - although both recover pretty quick once the exhaust fan stops. So I don't think I'll need a dehumidifier, I'll just be able to run the exhaust fan more often.