Hello Betsy!
Actually, nocturnal species such as grey tree frogs do not need uv exposure. Think about it, during the day the frogs are sleeping under leaves or logs or bark or things of that nature and the sunlight does not hit them. At night when they come out, there is still no light hitting them. They get all of their nutrients from their foods, which is why its important to dust their food with vitamins and calcium. Of course, having a uv light won't hurt, as long as they have plenty of places where they will not have to be exposed to it. I also believe that it would be best to release the froglets now rather than later. They need to learn how to hung on their own. Has this herpetologist collected data on how many frogs survived after he released them in the spring and on how many survived when released in the fall? I would also love to see this doctor's studies