Yes, a fan type heater would be beneficial, especially if inside a tent, as the humidity will go waaaay up and as you said, mould will just love those conditions. If using a heater it is also a good idea to have a separate fan to make sure the air is circulating and not just warm in one spot. Also, do not leave your lights on and shining on your harvested flowers in an effort to create warmth, as THC when exposed to direct light after harvest will degrade rapidly and result in ruined psycho-activity of your harvested flowers.
Hope this helps.... Organoman.