IMHO I don't think it's a good idea to release them, especially if they've spent their whole lives in captivity. They don't know how to hunt or find food without help. I'd be afraid they'd starve, or become some other predator's meal.
The conundrum is those animals don't have the necessary survival skills and will die living on their own / in the wild, so in this situation it would be cruel to set them free and sentence them to an early grave.
