hmm...I would say go for it. Why the hell not? =shrug= Really, if you don't like it, you can just take the earring out and leave it out after the con...the hole will go away. Earrings don't hurt to get pierced. It's more like a fuzzy, buzzing numb feeling after they get pierced. And you must swab them with a q-tip and peroxide to keep away infection. So long as you do that daily (twice is recommended I think), you'll be cool. ^^
Or of course, you could go for magnetic things.
Oh wait. Actually, when I got my ears pierced, they were pierced with sterling silver studs...no hoops. I'm not sure if that's what you must do, but if Onizuka has hoops, I think you'd better ask first before piercing.
Clip-on hoops are a pain in the ass and ugly, so far as I know