ive been doind this for about 13 years and with out a heater in the tent.
that doesnt mean i know best but,change clothes for bed and when you get up every time with new clean clothes(they should be dry) eat hearty ie-steak,potatos,chuncky type soups,full meals youll burn it all off.
youll need a real GOOD sleeping bag and in some cases we use 2,-15* or more at night.keep the feet dry and warm also keep the head warm sleeping or not (you can loose up to 80% of your body heat from the head).
and you do need somthing to get you off the ground while you sleep and a air mattress doesnt do it,you cant heat the air under you enough