My kids missed out last year as I didn't realize Nintendo was running a tournament (both TCG and video game) for Pokemon until the finals were upon us. I can't find any info on what Nintendo will be doing/running next week at PAX Oz. I even rang them up and they people I spoke to were clueless. Is this info available anywhere?
I did see the Gym Leader challenge which sounds fun.
According to the schedule, you have X & Y on Saturday at 1:30pm, and the TCG at 2pm every day, so you should be able to participate in at least one. For official Nintendo tourneys, I can't find any information on them either. Perhaps ask at their booth on Friday morning? Sorry I can't be much more helpful here.
As for the Pax Pokemon League, however, I can be extremely helpful. We're not an official Nintendo event, but the kids are more than welcome to come and earn some badges and prizes whenever they like, Just look for the bright green scarves.