Hi Beanie,
Will the tanks be getting a lot of light and battling algae? If so, a great option would be a group of American Flagfish, which are native, should probably be able to handle the temperature swings you'll have (although the high end could potentially be a problem) and are just about the best algae eating fish in existence. I put them in a 20 long that had green hair algae all through the plants and it was gone in a week. And you can spawn them in mops or just have some fry pop up if you have enough plants. If you keep them outside where rain is going directly into the tanks, just be sure the water doesn't get too soft, since they prefer hard water and can even handle it a bit brackish. They haven't bothered the bolbitis, anubias, java fern and java moss in their tank, but since they like plants they might bother more delicate plants.
For a small, non-native, you could do a group of 6+ (preferably 10+) Aphanius Mento killifish in a ten gallon. These are active little fish and the males get quite beautiful with dark color (black or dark blueish with white highlights). Their color actually looks a lot like some of the pygmy sunfish. Native to Turkey and other parts of the middle east, they are often kept outside in Europe. The cool temps should be fine and mine survived in tubs where the water probably hit the mid 80s. They eat algae as well, but probably not as voraciously as the Flagfish. They'll also eat dahpnia, frozen foods, etc., but mine get mostly green flakes. The Aphanius group in particular is known for handling extremes in temperature quite well. There are other species of Aphanius sometimes available, but Mentos are the most readily available and I think are about the most attractive as well.
Both can be found pretty reasonably on aquabid.
Post some picks when you get the tanks setup.