try booking 2 tickets on one flight, 2 tickets on another. Then have the party on the later flight same day standby for the earlier flight on the day of travel.
Worst case scenario you'll split up your party onto 2 different flights
Or if you can only get 2 tickets using miles, pay for 2 and use the other 2 at a later date/time.
For all the grumbling we see about using FF miles, I use mine all the time - usually VERY last minute for very popular destinations. I use them for MCO flights all the time. I flew home to Munich last year during World Cup, the busiest time for travel to Germany in a long time.