Another point to consider with respect to keeping warm in a tent is to use the smallest tent that suits your needs. I've found that using a pup tent for 3 small children and me kept us warm while people in travel trailers complained about being cold. Same for my hammock and a family in a tent-trailer. A smaller space means less air to warm up. You may also find that if you share a sleeping bag with your child, you will each be warmer.

Good Luck!

CamperMom