I would like to Host a Friends Tournament for fundraising at my Highschool. Help please

I am trying to fundraise for my AFJROTC unit to go on more drill trips next year. In doing so I think it would be really cool to host a league tourney and ask for entry money. winner can recieve something. doesnt have to be rp or skins. I just need help in trying to get them all on wifi that wouldnt crash. the school wifi would not allow students to play on their server. so what would i have to do?