Rat Terrier Breeding...?

I am expecting a litter on July 10, 2007. I have done a lot of research and I have been getting mixed answers, about the use of an extra heat source for the pups. I have heard that you do not need an extra heat source, and I have heard that it is a must or the pups will die. I would like to get more opinions. My house is approx. 65-75 degrees, the pups will be in a kiddie pool (whelping box), there will be plenty of blankets and towels in the pool for them. Any answers will be appreciated.