You will not have a good chance of getting the award tickets unless you pay the highest point rate for each award ticket which would be 720,000 points for 5 tickets. if you have 720,000 Skymiles then you have no problem.
You should also check with a consolidator, and possibly buy th 5 tickets for cash. Other aspects of your trip, hotel bookings can get m ore expensive as it gets closer to travel time, so locking in the dates by buying the tickets with a consolidator may save you more money on the lodging costs than if you wait until the last minute, If you do not have the 720,000 skymiles and the seats do not become avialalbe, then you may not be able to get to Brasil and miss out on the vacation.
RC