Birds like to perch on a high spot. Like
Icearstorm said, put some newspaper there and you'll have taken care of most of the problem with mess. In fact,
make a high spot (like on a top shelf) and the birds will most likely sit there.
Birds also fly toward light. If the room is somewhat darkened, and you have a small light on the cage, your birds will willingly fly back there. After a few days, you won't have to darken the room.
Most of all: sit there and watch. You'll soon see what the hazards and problems are, and you can adjust. Nothing is more important that just watching to see what the birds will do.
I'm glad you're letting your birds out of the cage. I think that a lot of problems (nutrition and health) are avoided when birds have plenty of exercise. That goes for humans, too! I'm on my way to the gym...