Where's the token bath-robe wizard throwing hacky sacks and shouting "magic missile! magic missile!"? Only thing I would do different is a larger playing area. All those people looked sort of crammed in there. Idea looks like fun though, a perfect chance to be ridiculous!
Handy hint time!
Some of those spears looked floppy as hell. Try cutting 8-12 inches off MAX and shooting them full of expanding foam. When it dries, trim it, and cap both ends. (I've also seen people use a metric ***-load of shredded paper) Then you won't feel like the Bob Dole of gladiators!