make this a one day deal and tell the selected players they need to show up with a C note in their pocket and play the damn game.
You don't need a four day event - most of the players don't care, they just want to play. And you can bet if one or two of the top 20 can't or won't show, the #21 and 22 players will jump on it with both feet.
Practice in late morning, have a big picnic lunch, afternoon break, and play games at 6pm and 8pm. veryone hangs out that night and goes home next day.
Its about the game wayne, not having 17 sponsers and four days worth of whatever