Rescueing two older dogs sounds awesome
My yorkie is bigger at 16 pounds and we have used a doggy door sense she was a year old. I love the doggy door a lot and am realizing how awesome it really was sense until Callie is completely healed and given the ok to run and jump she cant use hers and I have to take her out on the leash. Ours is a panel in our sliding glass door and some cold air does leak around it some. Most doggy doors that I know of have a little panel that slides over the doggy door to lock and close it which can be done during a time its very cold. If they are very small I would be worried about other animals or birds getting them.