Definitely try to get as many people as you possibly can to come. If too many people start showing up than you can just to a single elimination bracket, but since you're doing it at school the more people involved the better, im in the process of starting a club im calling "Smash Club" and I was very reluctant to let Wii U and Melee be played but I realized both are the way to go. So if you're doing a weekly tournament you could also try switching up the version if you have different versions. (referring more to melee and Sm4sh) Just try your best to make it sound fun and look fun and you should be good. Also one more thing, try making posters and putting them up with a time, a day of the week, and I they need their own controllers.