Holding a melee tournament when most of the melee-centric people aren't going to show doesn't make sense. Not holding a brawl tournament because there might be a lesser turnout doesn't make sense. Run brawl singles first thing, and then run brawl doubles alongside melee singles, so people can play in both melee and brawl singles. Run melee doubles and/or crews after that, and done. Avoid leaving a gap between brawl singles and doubles (IE take signups for both at the same time, and do a last call for doubles with the melee signups). This should minimize downtime, and allow for some sort of legitimate food break.
Also, people who have consoles should have to put their names on it with tape and whatnot, and tell the staff what TV it's on, and tell the staff when they leave. That way, if Wii's go missing, it should be easier to track down who has it, since the Wii will have been accounted for the whole time. All Wii's should also have Wiimotes brought with them, so it isn't such a pain to set up, and there's no confusion while doing so (IMO, what led to Wiiasco 2008).