Thanks all for your suggestions and discussion.
I'm in Melbourne. I have the room enclosed (which is the large majority of the year) except when the cooler is on.
I have some airflow options (ensuite door, windows, entrance door of the room) and the light is still pretty good. I tend to watch movies at night.
The kids use the room during the day for PS3/Wii. So there might be some light issues if the room is fully opened up. But I don't think the kids will be too fussed as long as the picture is decent.