One way to provide some extra warmth for the little naners in your greenhouse would be to get a black barrel, fill it with water, put a rigid screen over it, and set your plants on it. The water will absorb heat during the day and give it off during the night. Since heat rises, setting the plants on the screen over the water will result in the plants sitting in a relatively warm and humid updraft.
If you don't have a 55 gallon barrel, you could use a clustered group of four 5-gallon buckets. Paint them black, fill them with water, cover them with screens, and set one of your little naners on each bucket.
Best of luck with your naners, and welcome aboard!
