Point is, it's unrealistic to hold an event like this and not expect it to attract some petty crooks. Nobody's saying you have to personally deal with them - and getting a GM involved for, say, a simple pickpocket roleplay is a bit much - but where there's a market, there are going to be thieves, and where there's a sporting event, there are going to be drunks, probably angry ones at that. It has nothing to do with the tournament fees or three people attempting to run an event (which is an admirable feat, by the way). I'm just saying, let there be some potential for conflict here.
I get that it's annoying when some badguy comes barging in and tries to (censored) everyone up just because. That's probably the type you're worried about, right? Used to be, people would tell those off OOC and put them on the good ole' ignore list if they were being too disruptive, and they'd have their Epic Tavern Fights while the others played their night at Kada's (this was back when there was always someone at Kada's) like it wasn't happening. The forummers whining was what drove a lot of people to get the GMs involved, the way I remember it, in fact. Perhaps just /ignoring the burn-everything-down-all-glowy-eyed-like-while-laughing-maniacally gits is an unwritten rule we ought to bring back, hm?