The size sounds fine. If you get storms at all, you'll want to give them some protection and some shade. Look around for a small, used dog house. Put up on some blocks, it would work just fine. An outgrown child's playhouse is fun, too - both for you to decorate and look at and your birds to explore. You can generally come by those really cheaply, too - and you may find one with built-in nest boxes in the form of a play refrigerator!
